<SEC-DOCUMENT>0001047469-12-009455.txt : 20121011
<SEC-HEADER>0001047469-12-009455.hdr.sgml : 20121011
<ACCEPTANCE-DATETIME>20121011172217
ACCESSION NUMBER:		0001047469-12-009455
CONFORMED SUBMISSION TYPE:	424B5
PUBLIC DOCUMENT COUNT:		2
FILED AS OF DATE:		20121011
DATE AS OF CHANGE:		20121011

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CORPORATE OFFICE PROPERTIES TRUST
		CENTRAL INDEX KEY:			0000860546
		STANDARD INDUSTRIAL CLASSIFICATION:	REAL ESTATE INVESTMENT TRUSTS [6798]
		IRS NUMBER:				232947217
		STATE OF INCORPORATION:			MD
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		424B5
		SEC ACT:		1933 Act
		SEC FILE NUMBER:	333-180446
		FILM NUMBER:		121140528

	BUSINESS ADDRESS:	
		STREET 1:		6711 COLUMBIA GATEWAY DRIVE
		STREET 2:		SUITE 300
		CITY:			COLUMBIA
		STATE:			MD
		ZIP:			21046
		BUSINESS PHONE:		4432855400

	MAIL ADDRESS:	
		STREET 1:		6711 COLUMBIA GATEWAY DRIVE
		STREET 2:		SUITE 300
		CITY:			COLUMBIA
		STATE:			MD
		ZIP:			21046

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	CORPORATE OFFICE PROPERTIES TRUST INC
		DATE OF NAME CHANGE:	19980105

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ROYALE INVESTMENTS INC
		DATE OF NAME CHANGE:	19930328

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ROYALE REIT INC
		DATE OF NAME CHANGE:	19600201
</SEC-HEADER>
<DOCUMENT>
<TYPE>424B5
<SEQUENCE>1
<FILENAME>a2211329z424b5.htm
<DESCRIPTION>424B5
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Use these links to rapidly review the document<BR>
<A HREF="#bg11001_table_of_contents">  TABLE OF CONTENTS</A> <BR>
<A HREF="#bg11002_toc"> TABLE OF CONTENTS 2</A><BR></font>
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<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> CALCULATION OF REGISTRATION FEE  </B></FONT></P>

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<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
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<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
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<TD COLSPAN=9 VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
</TR>
<TR VALIGN="BOTTOM">
<TH ALIGN="CENTER" style="font-family:times;"><FONT SIZE=1><B>Title of Securities to be Registered</B></FONT><BR></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH ALIGN="CENTER" style="font-family:times;"><FONT SIZE=1><B>Amount to Be<BR>
Registered</B></FONT><BR></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH ALIGN="CENTER" style="font-family:times;"><FONT SIZE=1><B>Proposed Maximum<BR>
Offering Price Per<BR>
Share</B></FONT><BR></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH ALIGN="CENTER" style="font-family:times;"><FONT SIZE=1><B>Proposed Maximum<BR>
Aggregate Offering<BR>
Price</B></FONT><BR></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH ALIGN="CENTER" style="font-family:times;"><FONT SIZE=1><B>Amount of<BR>
Registration Fee<SUP>(1)</SUP></B></FONT><BR></TH>
</TR>
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<TD COLSPAN=9 VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
</TR>
<TR VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:5pt;text-indent:-5pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Common Shares of Beneficial Interest</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>8,625,000</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>$24.75</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>$213,468,750</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>$29,117.14</FONT></TD>
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<TD COLSPAN=9 VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;"><p style="font-family:times;margin-left:5pt;text-indent:-5pt;"> &nbsp;</TD>
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<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(1)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>A
filing fee of $29,117.14, calculated in accordance with Rule&nbsp;457(r), has been transmitted to the U.S. Securities and Exchange Commission in
connection with the securities offered by means of this prospectus supplement. </FONT></DD></DL>
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<P style="font-family:times;"><FONT SIZE=2>
<A HREF="#bg11001a_main_toc">Table of Contents</A> </FONT></P>

<P ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2><A
NAME="ba11001_filed_pursuant_to_rule__ba101409"> </A>
<A NAME="toc_ba11001_1"> </A>
<BR></FONT><FONT SIZE=2><B>  Filed Pursuant to Rule&nbsp;424(b)(5)<BR>  Registration No.&nbsp;333-180446    <BR>    </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT><FONT SIZE=2><B>PROSPECTUS SUPPLEMENT<BR>  </B></FONT><FONT SIZE=2>(To Prospectus dated March&nbsp;29, 2012) </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B>7,500,000 Shares  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B>
<IMG SRC="g694461.jpg" ALT="GRAPHIC" WIDTH="226" HEIGHT="130">
  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> Common Shares of Beneficial Interest  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=4><B>

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  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>We are offering 7,500,000 of our common shares. Our common shares are listed on the New York Stock Exchange under the symbol "OFC." The last reported sale price
on October&nbsp;10, 2012 was $25.36 per share. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B>Investing in our common shares involves risks. See "Risk Factors" beginning on page&nbsp;9 of our Annual Report on Form&nbsp;10-K for the year ended
December&nbsp;31, 2011 and in our Current Report on Form&nbsp;8-K filed with the Securities and Exchange Commission on October&nbsp;10, 2012 before buying our
shares.</B></FONT></P>

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<TH ALIGN="LEFT" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT><BR></TH>
<TH style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=2><B>Per Share </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=2><B>Total </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TH>
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<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:9pt;text-indent:-9pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Initial price to public</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>24.75</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>185,625,000</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
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<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:9pt;text-indent:-9pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Underwriting discounts and commissions</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>0.99</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>7,425,000</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
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<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:9pt;text-indent:-9pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Proceeds, before expenses, to us</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>23.76</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>178,200,000</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
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<P style="font-family:times;"><FONT SIZE=2>We have granted to the underwriters a 30-day option to purchase up to an additional 1,125,000 common shares from us at the public offering price,
less the underwriting discount. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B>None of the Securities and Exchange Commission, any state securities commission, or any other regulatory body has approved or disapproved of these securities or determined if
this prospectus supplement or the accompanying prospectus to which it relates is truthful or complete. Any representation to the contrary is a criminal offense.  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>The underwriters expect to deliver the shares on or about October&nbsp;16, 2012. </FONT></P>

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<TD style="font-family:times;"><BR><FONT SIZE=4><B>Wells Fargo Securities</B></FONT></TD>
<TD style="font-family:times;"><FONT SIZE=4><B><BR>&nbsp;</B></FONT></TD>
<TD ALIGN="CENTER" style="font-family:times;"><BR><FONT SIZE=4><B>J.P. Morgan</B></FONT></TD>
<TD style="font-family:times;"><FONT SIZE=4><B><BR>&nbsp;</B></FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><BR><FONT SIZE=4><B>Barclays</B></FONT></TD>
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<TD VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=3><B>KeyBanc Capital Markets</B></FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=3><B><BR>&nbsp;</B></FONT></TD>
<TD ALIGN="CENTER" VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=3><B>Piper Jaffray</B></FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=3><B><BR>&nbsp;</B></FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=3><B>RBC Capital Markets</B></FONT></TD>
</TR>
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<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2><B>Baird</B></FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="CENTER" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2><B>Comerica Securities</B></FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2><B>PNC Capital Markets&nbsp;LLC</B></FONT></TD>
</TR>
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<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2><B>Stifel Nicolaus Weisel</B></FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD COLSPAN=3 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2><B>SunTrust Robinson Humphrey<BR> </B></FONT></TD>
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&nbsp;&nbsp;&nbsp;
</b></font></p><p align=center style="font-family:times;"><FONT SIZE=2><B>Prospectus supplement dated October&nbsp;11, 2012.</B></FONT></P>

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<P style="font-family:times;"><FONT SIZE=2><A
NAME="BG11001A_main_toc"></A>
<A HREF="#bg11001a_main_toc">Table of Contents</A> </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT><FONT SIZE=2><B>You should rely only on the information contained in, or incorporated by reference in, this prospectus supplement and the accompanying
prospectus or any free writing prospectus prepared by or on behalf of us. We have not, and the underwriters have not, authorized anyone to provide you with different information. If anyone provides
you with different or inconsistent information you should not rely on it. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale
is not permitted. You should not assume that the information contained in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference is accurate as of any date
other than the dates of the specific information. Our business, financial condition, results of operations and prospectus may have changed since those respective dates.</B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="bg11001_table_of_contents"> </A>
<BR></FONT><FONT SIZE=4><B>  TABLE OF CONTENTS  <BR>  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="bg11001_prospectus_supplement"> </A></FONT> <FONT SIZE=2><B>  Prospectus Supplement    <BR>    </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2><A
NAME="BG11001_TOC"></A> </FONT></P>
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<p style="font-family:times;"></FONT></P>

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<TH ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=2><B>Page </B></FONT></TH>
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<TD style="font-family:times;"><A HREF="#ca11001_about_this_prospectus_supplement"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>About This Prospectus Supplement</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#ca11001_about_this_prospectus_supplement"><FONT SIZE=2>S-1</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#ca11001_forward-looking_statements"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Forward-Looking Statements</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#ca11001_forward-looking_statements"><FONT SIZE=2>S-1</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#ca11001_the_offering"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>The Offering</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#ca11001_the_offering"><FONT SIZE=2>S-3</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#ca11001_the_company"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>The Company</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#ca11001_the_company"><FONT SIZE=2>S-5</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#ca11001_recent_developments"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Recent Developments</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#ca11001_recent_developments"><FONT SIZE=2>S-6</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#ca11001_use_of_proceeds"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Use of Proceeds</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#ca11001_use_of_proceeds"><FONT SIZE=2>S-7</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#ca11001_capitalization"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Capitalization</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#ca11001_capitalization"><FONT SIZE=2>S-8</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#ca11001_description_of_common_shares"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Description of Common Shares</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#ca11001_description_of_common_shares"><FONT SIZE=2>S-9</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#ca11001_additional_federal_income_tax_matters"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Additional Federal Income Tax Matters</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#ca11001_additional_federal_income_tax_matters"><FONT SIZE=2>S-10</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#cc11001_underwriting"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Underwriting</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#cc11001_underwriting"><FONT SIZE=2>S-11</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#Legal"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Legal Matters</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#Legal"><FONT SIZE=2>S-18</FONT></A></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><A HREF="#INFO"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Where You Can Find More Information</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><A HREF="#INFO"><FONT SIZE=2>S-18</FONT></A></TD>
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<BR></FONT><FONT SIZE=2><B>  Prospectus    <BR>    </B></FONT></P>
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<p style="font-family:times;"></FONT></P>

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<TH style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TH>
<TH ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=2><B>Page </B></FONT></TH>
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<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Abt"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>About this Prospectus</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Abt"><FONT SIZE=2>3</FONT></A></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#For"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Forward-Looking Statements</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#For"><FONT SIZE=2>3</FONT></A></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Sum"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Summary</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Sum"><FONT SIZE=2>5</FONT></A></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Our"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Our Company</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Our"><FONT SIZE=2>5</FONT></A></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Use"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Use of Proceeds</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Use"><FONT SIZE=2>6</FONT></A></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Ratios"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Ratios of Earnings to Combined Fixed Charges and Preferred Share Dividends</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Ratios"><FONT SIZE=2>6</FONT></A></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Desp_shares"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Description of Shares</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Desp_shares"><FONT SIZE=2>6</FONT></A></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Desp_Warr"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Description of Warrants</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Desp_Warr"><FONT SIZE=2>18</FONT></A></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Federal"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Federal Income Tax Matters</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Federal"><FONT SIZE=2>19</FONT></A></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Plan"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Plan of Distribution</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Plan"><FONT SIZE=2>32</FONT></A></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Expert"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Experts</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Expert"><FONT SIZE=2>33</FONT></A></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Sell_sec"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Selling Securityholders</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Sell_sec"><FONT SIZE=2>33</FONT></A></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Leg_Mtr"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Legal Matters</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Leg_Mtr"><FONT SIZE=2>34</FONT></A></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Where"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Where You Can Find More Information</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Where"><FONT SIZE=2>34</FONT></A></TD>
</TR>
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<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
terms "COPT," "Company," "we," "our" and "us" refer to Corporate Office Properties Trust, individually or together with its subsidiaries, including Corporate Office
Properties,&nbsp;L.P., which is referred to as our operating partnership, and our predecessors, unless the context suggests otherwise. The term "you" refers to a prospective investor. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-i</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>
<A HREF="#bg11001a_main_toc">Table of Contents</A> </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="ca11001_about_this_prospectus_supplement"> </A>
<A NAME="toc_ca11001_1"> </A>
<BR></FONT><FONT SIZE=4><B>  ABOUT THIS PROSPECTUS SUPPLEMENT  <BR>  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We are providing information to you about this offering of our common shares in two parts. The first part is this
prospectus supplement, which provides the specific details regarding this offering. The second part is the accompanying prospectus, which provides general information. Generally, when we refer to this
"prospectus," we are referring to both documents combined, as well as to the documents incorporated by reference in this prospectus supplement and the accompanying prospectus. Some of the information
in the accompanying prospectus may not apply to this offering. If information in this prospectus supplement is inconsistent with the accompanying prospectus, you should rely on this prospectus
supplement. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="ca11001_forward-looking_statements"> </A>
<A NAME="toc_ca11001_2"> </A>
<BR></FONT><FONT SIZE=4><B>  FORWARD-LOOKING STATEMENTS  <BR>  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This prospectus supplement, the accompanying prospectus and our documents incorporated by reference in this prospectus
supplement and the accompanying prospectus contain "forward-looking" statements, within the meaning of Section&nbsp;27A of the Securities Act of 1933, as amended (the "Securities Act"), and
Section&nbsp;21E of the Securities Exchange Act of 1934, as amended (the "Exchange Act") that are based on our current expectations, estimates and projections about future events and financial
trends affecting the financial condition of our business. Forward-looking statements can be identified by the use of words such as "may," "will," "should," "could," "believe," "anticipate," "expect,"
"estimate," "plan" or other comparable terminology. Forward-looking statements are inherently subject to risks and uncertainties, many of which we cannot predict with accuracy and some of which we
might not even anticipate. Although we believe that the expectations, estimates and projections reflected in such forward-looking statements are based on reasonable assumptions at the time made, we
can give no assurance that these expectations, estimates and projections will be achieved. Accordingly, actual results may differ materially from those addressed in the forward-looking statements. We
caution readers that forward-looking statements reflect our opinion only as of the date on which they were made. You should not place undue reliance on forward-looking statements. We undertake no
obligation to publicly update forward-looking statements, whether as a result of new information, future events or otherwise. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Important
factors that may affect these expectations, estimates or projections expressed in forward-looking statements include, but are not limited
to:</FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>general economic and business conditions, which will, among other things, affect office property and data center demand
and rents, tenant creditworthiness, interest rates, financing availability and property values; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>adverse changes in the real estate markets, including, among other things, increased competition with other companies; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>governmental actions and initiatives, including risks associated with the impact of a government shutdown and budgetary
reductions or impasses, such as a reduction in rental revenues, non-renewal of leases and/or a curtailment of demand for additional space by our strategic customers; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our ability to borrow on favorable terms; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>risks of real estate acquisition and development activities, including, among other things, risks that development
projects may not be completed on schedule, that tenants may not take occupancy or pay rent or that development or operating costs may be greater than anticipated; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our ability to sell properties included in our Strategic Reallocation Plan (as defined herein); </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>risks of investing through joint venture structures, including risks that our joint venture partners may not fulfill their
financial obligations as investors or may take actions that are inconsistent with our objectives; </FONT></DD></DL>
</UL>
<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-1</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2><A
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<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>changes in our plans for properties or views of market economic conditions or failure to obtain development rights, either
of which could result in recognition of impairment losses; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our ability to satisfy and operate effectively under federal income tax rules relating to real estate investment trusts
and partnerships; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the dilutive effects of issuing additional common shares; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our ability to achieve projected results; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>environmental requirements; and </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the other factors described beginning on page&nbsp;9 of our Annual Report on Form&nbsp;10-K for the year
ended December&nbsp;31, 2011 under the heading "Risk Factors" and in our Current Report on Form&nbsp;8-K filed with the Securities and Exchange Commission on October&nbsp;10, 2012. </FONT></DD></DL>
</UL>
<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-2</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2><A
HREF="#bg11001a_main_toc">Table of Contents</A></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="ca11001_the_offering"> </A>
<A NAME="toc_ca11001_3"> </A>
<BR></FONT><FONT SIZE=4><B>  THE OFFERING  <BR>  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The following is a brief summary of certain terms of this offering. </FONT></P>
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<TD style="font-family:times;"><FONT SIZE=2>Issuer</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>Corporate Office Properties Trust</FONT></TD>
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<TD style="font-family:times;"><BR><FONT SIZE=2>Common shares offered</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=2>7,500,000 shares</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><BR><FONT SIZE=2>Additional option to purchase shares</FONT></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD style="font-family:times;"><BR><FONT SIZE=2>1,125,000 shares</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><BR><FONT SIZE=2>Common&nbsp;shares&nbsp;to&nbsp;be&nbsp;outstanding immediately after this offering(1)</FONT></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD style="font-family:times;"><BR><FONT SIZE=2>79,667,410</FONT></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><BR><FONT SIZE=2>Use of proceeds</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=2>We intend to contribute the net proceeds from this offering to our operating partnership to repay borrowings under our unsecured revolving credit facility, which were approximately $115.0&nbsp;million
as of October&nbsp;9, 2012, and for general corporate purposes. See "Use of Proceeds."</FONT></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><BR><FONT SIZE=2>Distribution policy</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=2>We have declared and paid consecutive quarterly dividends on our common shares for over 14&nbsp;years, and our current quarterly dividend payment is $0.275 per share. We intend to continue to make
quarterly distributions to holders of our common shares out of our earnings. Among other things, the per share amounts of future distributions may depend on the number of our common and preferred shares outstanding from time-to-time. As of the date
of this offering, our outstanding preferred shares, which rank senior to our common shares with respect to payment of dividends, include 2,000,000 of our 7.5% Series&nbsp;H Cumulative Redeemable Preferred Shares, 3,450,000 of our 7.625% Series&nbsp;J
Cumulative Redeemable Preferred Shares, 531,667 of our 5.6% Series&nbsp;K Cumulative Redeemable Preferred Shares and 6,900,000 of our Series&nbsp;L Cumulative Preferred Shares.</FONT></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><BR><FONT SIZE=2>Listing</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=2>Our common shares are listed on the NYSE under the symbol "OFC."</FONT></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><BR><FONT SIZE=2>Restrictions on ownership</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=2>To assist us in maintaining our qualification as a REIT, our Declaration of Trust provides that no person, other than a person that has received an exemption, may own directly or indirectly, or be
deemed to own by virtue of certain attribution provisions of the Internal Revenue Code of 1986, as amended, more than 9.8%, in value or number of shares, whichever is more restrictive, of the outstanding common shares. For more information, see
"Description of Shares&#151;Restrictions on Ownership and Transfer" in the accompanying prospectus.</FONT></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><BR><FONT SIZE=2>Tax consequences</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=2>The federal income tax consequences of purchasing, owning and disposing of our common shares are summarized in "Additional Federal Income Tax Matters" in this prospectus supplement and in "Federal
Income Tax Matters" in the accompanying prospectus.</FONT></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><BR><FONT SIZE=2>Settlement date</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=2>Delivery of the common shares will be made against payment therefor on or about October&nbsp;16, 2012.</FONT></TD>
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<TD style="font-family:times;"><FONT SIZE=2>Transfer agent</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>The transfer agent for our common shares is Wells Fargo Bank, N.A.</FONT></TD>
</TR>
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<TD style="font-family:times;"><BR><FONT SIZE=2>Conflicts of Interest</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=2>As described in "Use of Proceeds," we expect to contribute the net proceeds from this offering to our operating partnership to repay borrowings under our unsecured revolving credit facility. Affiliates
of Wells Fargo Securities,&nbsp;LLC, J.P. Morgan Securities&nbsp;LLC, Barclays Capital&nbsp;Inc., KeyBanc Capital Markets&nbsp;Inc., RBC Capital Markets,&nbsp;LLC, Comerica Securities,&nbsp;Inc., PNC Capital Markets&nbsp;LLC and SunTrust Robinson
Humphrey,&nbsp;Inc. are lenders under our revolving credit facility and will receive a portion of the net proceeds from this offering through the repayment of those borrowings. See "Underwriting."</FONT></TD>
</TR>
<TR VALIGN="TOP">
<TD style="font-family:times;"><BR><FONT SIZE=2>Risk Factors</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2><BR>&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><BR><FONT SIZE=2>See "Risk Factors" beginning on page&nbsp;9 of our Annual Report on Form&nbsp;10-K for the year ended December&nbsp;31, 2011 and in our Current Report on Form&nbsp;8-K filed with the Securities and
Exchange Commission on October&nbsp;10, 2012, both of which are incorporated by reference into this prospectus supplement, for other information you should consider before buying our common shares.</FONT></TD>
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<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(1)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>The
number of common shares to be outstanding after this offering is based on 72,167,410&nbsp;common shares outstanding as of October&nbsp;9, 2012, and
assumes no exercise of the underwriters' option to purchase up to an additional 1,125,000 common shares. </FONT></DD></DL>
<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-4</FONT></P>

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HREF="#bg11001a_main_toc">Table of Contents</A></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="ca11001_the_company"> </A>
<A NAME="toc_ca11001_4"> </A>
<BR></FONT><FONT SIZE=4><B>  THE COMPANY  <BR>  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We are an office real estate investment trust ("REIT") that focuses primarily on serving the specialized requirements
of strategic customers in the United States Government and defense information technology sectors. We acquire, develop, manage and lease office and data center properties that are typically
concentrated in large office parks primarily located adjacent to government demand drivers and/or in office markets that we believe possess growth opportunities. As of June&nbsp;30, 2012, our
investments in real estate included the following:</FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>228 operating office properties totaling 19.8&nbsp;million square feet; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>nine office properties under construction or redevelopment that we estimate will total approximately 1.1&nbsp;million
square feet upon completion, including two partially operational properties included above; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>land held or under pre-construction totaling 2,303 acres (including 583 controlled but not owned) that we
believe are potentially developable into approximately 20.1&nbsp;million square feet; and </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>a partially operational, wholesale data center which upon completion and stabilization is expected to have a critical load
of 18 megawatts. </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
focus on customers in the United States Government and defense information technology sectors is a key aspect of our customer strategy. A high percentage of our revenue is
concentrated with these customers, and we expect to further increase this concentration level through our:</FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>properties' proximity to government demand drivers (such as military installations) in various regions of the country and
our willingness to expand to other regions where demand exists; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>strong relationships and reputation for high service levels that we have forged over the years and continue to emphasize; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>depth of collective team knowledge, experience and capabilities in developing and operating single user data centers and
securing properties that meet the United States Government's Force Protection requirements; and </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>property dispositions under the plan we implemented in 2011 to dispose of office properties and land that are no longer
closely aligned with our strategy (the "Strategic Reallocation Plan"), as discussed in our 2011 Annual Report on Form&nbsp;10-K for the year ended December&nbsp;31, 2011. </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We
believe that we differentiate ourselves by being a real estate company that does not view space in properties merely as a commodity. We focus on providing a level of service that
exceeds customer expectations both in terms of the quality of the space we provide and our level of responsiveness to customers' (or tenants') needs. In 2011, we won the CEL&nbsp;&amp;
Associates,&nbsp;Inc. award for quality service and tenant satisfaction among nationwide office operators in the large owner category for the eighth consecutive year. We believe that operating with
such an emphasis on customer service enables us to be the landlord of choice, with high quality customers, and contributes to high levels of customer loyalty and retention. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
five executive officers have an average of 26&nbsp;years of real estate experience. In addition, as of September&nbsp;30, 2012, our executive officers and trustees collectively
owned 5.5% of our common equity interests, which includes ownership of outstanding common shares and common units of our operating partnership that are exchangeable, at our option, into common shares. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
executive offices are located at 6711 Columbia Gateway Drive, Suite&nbsp;300, Columbia, Maryland 21046 and our telephone number is (443)&nbsp;285-5400. You can
contact us by e-mail at </FONT><FONT SIZE=2><I>ir@copt.com</I></FONT><FONT SIZE=2>, or by visiting our website, </FONT><FONT SIZE=2><I>www.copt.com</I></FONT><FONT SIZE=2>. The
information contained on our website is not part of this prospectus supplement or the accompanying prospectus. Our reference to our website is intended to be an inactive textual reference only. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-5</FONT></P>

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HREF="#bg11001a_main_toc">Table of Contents</A></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="ca11001_recent_developments"> </A>
<A NAME="toc_ca11001_5"> </A>
<BR></FONT><FONT SIZE=4><B>  RECENT DEVELOPMENTS  <BR>  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Since June&nbsp;30, 2012 and through the date of this prospectus supplement, we completed the
following:</FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>On July&nbsp;11, 2012, we acquired 13857 McLearen Road, a 202,000 square foot office property in Herndon, Virginia that
was 100% leased, for $49.0&nbsp;million. </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>On July&nbsp;24, 2012, we sold 23 operating properties totaling 1.4&nbsp;million square feet and a
six-acre land parcel in the Baltimore/Washington Corridor and Greater Baltimore regions for an aggregate sale price of $162&nbsp;million. </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>On August&nbsp;3, 2012, we entered into an unsecured term loan agreement with a group of lenders for which Wells Fargo
Securities,&nbsp;LLC acted as sole arranger and sole book runner, Wells Fargo Bank, National Association acted as administrative agent and Capital One, N.A. acted as documentation agent. We borrowed
$120&nbsp;million under the term loan, with a right for us to borrow an additional $80&nbsp;million provided that there is no default under the agreement. The term loan matures on August&nbsp;2,
2019. The variable interest rate on the loan is based on the LIBOR rate (customarily the 30-day rate) plus 2.10% to 2.60%, as determined by our leverage levels. </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>On August&nbsp;6, 2012, we redeemed all of our Series&nbsp;G Preferred Shares of beneficial interest at a price of
$25.00 per share, or $55.0&nbsp;million in the aggregate, plus accrued and unpaid dividends thereon through the date of redemption. </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>On August&nbsp;10, 2012, we exercised our right to reduce the lenders' aggregate commitment under our unsecured
revolving credit facility from $1.0&nbsp;billion to $800&nbsp;million, with a right, subject to certain conditions, for us to increase the lenders' aggregate commitment to $1.3&nbsp;billion. </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>In September 2012, we executed a lease with a strategic tenant for 115,000 square feet, encompassing all of our 7205
Riverwood Road development, plus an adjacent property ("Riverwood"). Riverwood is part of Rivers Corporate Park in Columbia, Maryland, located within a 10-mile radius of Fort Meade. The
strategic tenant plans to occupy the property in late 2013 or early 2014. </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>On September&nbsp;20, 2012, we completed a new lease with a high-growth commercial colocation provider at
our DC-6 data center in Manassas, Virginia. The lease provides for an initial commitment of one megawatt (MW), plus opportunities for expansion. </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>On September&nbsp;24, 2012, our Board of Trustees approved a plan by management to shorten the holding period for office
properties and developable land in Greater Philadelphia, Pennsylvania (the "Greater Philadelphia Properties") because the properties no longer meet our strategic investment criteria. We determined
that the carrying amounts of the Greater Philadelphia Properties will not likely be recovered from the cash flows from the operations and sales of such properties over the likely remaining holding
period. Accordingly, during the three months ending September&nbsp;30, 2012, we recognized aggregate non-cash impairment losses of approximately $46&nbsp;million for the amounts by
which the carrying values of the Greater Philadelphia Properties exceed their respective estimated fair values. These losses contemplate our expectation that we will incur future cash expenditures of
approximately $25&nbsp;million to complete our redevelopment of the properties. </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>On October&nbsp;5, 2012, we leased an aggregate of approximately 363,000 square feet in a newly constructed property and
two properties to be constructed in Huntsville, Alabama. </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>On October&nbsp;10, 2012, we filed with the Securities and Exchange Commission a Current Report on
Form&nbsp;8-K, which is incorporated in this prospectus supplement by reference, in which we disclosed (i)&nbsp;certain impairments that we expect to recognize during the three months
ended September&nbsp;30, 2012 with respect to our properties in Colorado Springs, Colorado, and (ii)&nbsp;revised expectations for our operating results for the three months ended
September&nbsp;30, 2012 and the year ending December&nbsp;31, 2012. </FONT></DD></DL>
</UL>
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<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="ca11001_use_of_proceeds"> </A>
<A NAME="toc_ca11001_6"> </A>
<BR></FONT><FONT SIZE=4><B>  USE OF PROCEEDS  <BR>  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We intend to contribute to our operating partnership the net proceeds from the sale of the common shares,
approximately $178.0&nbsp;million after deducting the underwriting discounts and commissions and our expenses related to this offering, or approximately $204.7&nbsp;million if the underwriters'
option to purchase additional shares is exercised in full. We intend to use the net proceeds from this offering to repay borrowings under our unsecured revolving credit facility and for general
corporate purposes. The weighted average interest rate on this facility was 2.24% as of June&nbsp;30, 2012 and $195.0&nbsp;million was outstanding as of that date. As of October&nbsp;9, 2012,
the weighted average interest rate on this facility was 2.19% and $115.0&nbsp;million was outstanding. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Affiliates
of Wells Fargo Securities,&nbsp;LLC, J.P. Morgan Securities&nbsp;LLC, Barclays Capital&nbsp;Inc., KeyBanc Capital Markets&nbsp;Inc., RBC Capital Markets,&nbsp;LLC,
Comerica Securities,&nbsp;Inc., PNC Capital Markets&nbsp;LLC and SunTrust Robinson Humphrey,&nbsp;Inc. are lenders under our unsecured revolving credit facility. As described above, we intend to
use the net proceeds of this offering to repay borrowings outstanding under our unsecured revolving credit facility. Because affiliates of Wells Fargo Securities,&nbsp;LLC, J.P.&nbsp;Morgan
Securities&nbsp;LLC, Barclays Capital&nbsp;Inc., KeyBanc Capital Markets&nbsp;Inc., RBC Capital Markets,&nbsp;LLC, Comerica Securities,&nbsp;Inc., PNC Capital Markets&nbsp;LLC and SunTrust
Robinson Humphrey,&nbsp;Inc. are lenders under our unsecured revolving credit facility, those affiliates will receive a portion of the net proceeds from this offering through the repayment of those
borrowings. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-7</FONT></P>

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<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="ca11001_capitalization"> </A>
<A NAME="toc_ca11001_7"> </A>
<BR></FONT><FONT SIZE=4><B>  CAPITALIZATION  <BR>  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The following table sets forth our capitalization as of June&nbsp;30, 2012:</FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>on a historical basis; and </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>on an as adjusted basis to reflect the sale of 7,500,000 common shares of beneficial interest offered by us at the public
offering price of $24.75 per share, less underwriting discounts and commissions and offering expenses payable by us, and the application of net proceeds as set forth in the "Use of Proceeds" section,
but does not reflect the impact of items discussed in "Recent Developments." </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
information set forth in the following table should be read in conjunction with the consolidated financial statements and the notes thereto in our Annual Report on
Form&nbsp;10-K for the year ended December&nbsp;31, 2011, and in our Quarterly Report on Form&nbsp;10-Q for the quarter ended June&nbsp;30, 2012, which is incorporated
by reference herein. </FONT></P>
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<TR VALIGN="BOTTOM">
<TH ALIGN="LEFT" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT><BR></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=8 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>As of June&nbsp;30, 2012 </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
</TR>
<TR VALIGN="BOTTOM">
<TH ALIGN="LEFT" style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT><BR></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>Historical </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>Adjustments(1) </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>As<BR>
Adjusted </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
</TR>
<TR VALIGN="BOTTOM">
<TH ALIGN="LEFT" style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT><BR></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=8 ALIGN="CENTER" style="font-family:times;"><FONT SIZE=1><B>(Dollars in thousands)</B></FONT><BR></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Cash and cash equivalents</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>4,702</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>4,702</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Restricted cash and marketable securities</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>22,632</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>22,632</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR style="font-size:1.5pt;" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:20pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Total cash and restricted cash and marketable securities</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>27,334</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>27,334</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR style="font-size:1.5pt;" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Debt, net</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>2,191,851</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>(177,950</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>)</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>2,013,901</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR style="font-size:1.5pt;" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Equity:</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Corporate Office Properties Trust's shareholders' equity:</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:30pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Preferred Shares of beneficial interest at liquidation preference ($0.01 par value; 25,000,000 shares authorized, 15,021,667 shares issued and
outstanding)</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>388,833</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>388,833</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:30pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Common Shares of beneficial interest ($0.01 par value; 125,000,000 authorized, 72,084,932 shares issued and outstanding on a historical basis, 79,584,932
shares issued and outstanding on an as adjusted basis)</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>721</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>75</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>796</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:30pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Additional paid-in capital(2)</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>1,450,923</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>177,875</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>1,628,798</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:30pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Cumulative distributions in excess of net income</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>(562,678</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>)</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>(562,678</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>)</FONT></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:30pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Accumulated other comprehensive loss</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>(3,717</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>)</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>(3,717</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>)</FONT></TD>
</TR>
<TR style="font-size:1.5pt;" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:40pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Total Corporate Office Properties Trust's shareholders' equity</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>1,274,082</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>177,950</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>1,452,032</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR style="font-size:1.5pt;" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Noncontrolling interests in subsidiaries:</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:20pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Common units in the Operating Partnership</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>52,152</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>52,152</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:20pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Preferred units in the Operating Partnership</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>8,800</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>8,800</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:20pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Other consolidated entities</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>18,315</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>18,315</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR style="font-size:1.5pt;" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:30pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Total noncontrolling interests in subsidiaries</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>79,267</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>79,267</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR style="font-size:1.5pt;" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:solid #000000 1.0pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
</TR>
<TR BGCOLOR="White" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Total equity</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>1,353,349</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>177,950</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>1,531,299</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR style="font-size:1.5pt;" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Total capitalization</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>3,545,200</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&#151;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>3,545,200</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR style="font-size:1.5pt;" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD COLSPAN=2 ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
</TR>
</TABLE></DIV>
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<DIV style="padding:0pt;position:relative;text-align:left;margin-left:10%;">
 <DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(1)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>Assumes
no exercise of the underwriters' option to purchase up to an additional 1,125,000 common shares.
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(2)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>Represents
additional paid-in capital, net of estimated issuance costs. </FONT></DD></DL>
 </DIV>
 <P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-8</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2><A
HREF="#bg11001a_main_toc">Table of Contents</A></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="ca11001_description_of_common_shares"> </A>
<A NAME="toc_ca11001_8"> </A>
<BR></FONT><FONT SIZE=4><B>  DESCRIPTION OF COMMON SHARES  <BR>  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;A summary of the terms and provisions of our common shares is contained in "Description of Shares&nbsp;&#151;
Common Shares" in the accompanying prospectus. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-9</FONT></P>

<HR NOSHADE>
<P style='font-family:times;page-break-before:always'></p>
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<P style="font-family:times;"><FONT SIZE=2><A
HREF="#bg11001a_main_toc">Table of Contents</A></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="ca11001_additional_federal_income_tax_matters"> </A>
<A NAME="toc_ca11001_9"> </A>
<BR></FONT><FONT SIZE=4><B>  ADDITIONAL FEDERAL INCOME TAX MATTERS  <BR>  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The following summary of additional Federal income tax considerations regarding an investment in our common shares is
based on current law, is for general information only and is not tax advice. This summary supplements the discussion set forth in the accompanying prospectus under the heading "Federal Income Tax
Matters." This discussion does not purport to deal with all aspects of taxation that may be relevant to particular investors in light of their personal investment or tax circumstances. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Each
prospective purchaser is advised to consult his or her own tax advisor regarding the specific tax consequences to him or her of the purchase, ownership and sale of the common
shares and of our election to be taxed as a REIT, including the Federal, state, local, foreign income and other tax consequences of such purchase, ownership, sale and election, and of potential
changes in applicable tax laws. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Potential Changes to Tax Rates.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Because we qualify as a REIT, distributions made to our U.S. shareholders out of our
earnings and profits will
generally constitute dividends taxable as ordinary income except to the extent that such distributions are designated as capital gains. Under current law, the highest marginal individual income tax
rate on ordinary income is 35% while the highest individual income tax rate on long-term capital gains is generally 15%. In the absence of legislation to the contrary, starting in 2013,
the highest marginal individual income tax rate on ordinary income will be 39.6% while the highest individual income tax rate on long-term capital gains will generally be 20%. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Guidance Relating to Foreign Accounts.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;On February&nbsp;8, 2012, the Treasury Department issued proposed regulations
relating to the Foreign
Account Tax Compliance provisions of the Hiring Incentives to
Restore Employment Act (known as "FATCA") which was enacted in March of 2010. FATCA generally imposes a 30% withholding tax on dividends on, and gross proceeds from the sale or other disposition of,
COPT's shares of beneficial interests, including our common shares, if paid to a foreign entity unless (i)&nbsp;if the foreign entity is a "foreign financial institution," the foreign entity
undertakes certain due diligence, reporting, withholding, and certification obligations, (ii)&nbsp;if the foreign entity is not a "foreign financial institution," the foreign entity identifies
certain of its U.S. investors, or (iii)&nbsp;the foreign entity is otherwise excepted under FATCA. Under the proposed regulations, withholding is required (i)&nbsp;with respect to dividends on the
common shares beginning on January&nbsp;1, 2014, and (ii)&nbsp;with respect to gross proceeds from a sale or other disposition of the common shares that occurs on or after January&nbsp;1, 2015. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Notwithstanding
the foregoing, the proposed regulations will not be effective until issued in final form. There can be no assurance either as to when final regulations relating to FATCA
will be issued or as to the particular form that those final regulations might take. If withholding is required under FATCA on a payment related to the common shares, investors that otherwise would
not be subject to withholding (or that otherwise would be entitled to a reduced rate of withholding) on such payment generally will be required to seek a refund or credit from the IRS to obtain the
benefit of such exemption or reduction (provided that such benefit is available). The discussion in this section replaces and supersedes the final two paragraphs under "Federal Income Tax
Matters&nbsp;&#151; Taxation of Shareholders&nbsp;&#151; Taxation of Foreign Shareholders" in the accompanying prospectus. Prospective purchasers of common shares should consult
their tax advisors regarding the effect of FATCA in their particular circumstances. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-10</FONT></P>

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<P style='font-family:times;page-break-before:always'></p>
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</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>
<A HREF="#bg11001a_main_toc">Table of Contents</A> </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="cc11001_underwriting"> </A>
<A NAME="toc_cc11001_1"> </A>
<BR></FONT><FONT SIZE=4><B>  UNDERWRITING  <BR>  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Subject to the terms and conditions described in an underwriting agreement among us and the underwriters named below,
for whom Wells Fargo Securities,&nbsp;LLC, J.P.&nbsp;Morgan Securities&nbsp;LLC and Barclays Capital&nbsp;Inc. are acting as representatives, we have agreed to sell to the underwriters, and
the underwriters severally have agreed to purchase from us, the number of shares listed opposite their names below. </FONT></P>
 <DIV style="padding:0pt;position:relative;width:70%;margin-left:15%;">
<p style="font-family:times;"></FONT></P>

<!-- COMMAND=ADD_TABLEWIDTH,"100%" -->

<!-- User-specified TAGGED TABLE -->
<DIV ALIGN="CENTER"><TABLE width="100%"  BORDER=0 CELLSPACING=0 CELLPADDING=0>
<TR><!-- TABLE COLUMN WIDTHS SET -->
<TD WIDTH="" style="font-family:times;"></TD>
<TD WIDTH="12pt" style="font-family:times;"></TD>
<TD WIDTH="65pt" style="font-family:times;"></TD>
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<TR VALIGN="BOTTOM">
<TH NOWRAP  ALIGN="LEFT" style="font-family:times;"><DIV style="border-bottom:solid #000000 1.0pt;margin-bottom:0pt;width:55pt;"><FONT SIZE=2><B>Underwriter

<!-- COMMAND=ADD_SCROPPEDRULE,55pt -->

 </B></FONT></DIV></TH>
<TH style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TH>
<TH ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=2><B>Number of<BR>
Shares </B></FONT></TH>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Wells Fargo Securities,&nbsp;LLC</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>1,950,000</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>J.P. Morgan Securities&nbsp;LLC</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>1,950,000</FONT></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Barclays Capital&nbsp;Inc.&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>975,000</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>KeyBanc Capital Markets&nbsp;Inc.&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>500,000</FONT></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Piper Jaffray&nbsp;&amp;&nbsp;Co.&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>500,000</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>RBC Capital Markets,&nbsp;LLC</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>500,000</FONT></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Robert&nbsp;W. Baird&nbsp;&amp;&nbsp;Co. Incorporated</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>225,000</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Comerica Securities,&nbsp;Inc.&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>225,000</FONT></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>PNC Capital Markets&nbsp;LLC</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>225,000</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Stifel, Nicolaus&nbsp;&amp; Company, Incorporated</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>225,000</FONT></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>SunTrust Robinson Humphrey,&nbsp;Inc.&nbsp;</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>225,000</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:20pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Total</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>7,500,000</FONT></TD>
</TR>
<TR style="font-size:1.5pt;" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD VALIGN="BOTTOM" style="font-family:times;">&nbsp;</TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;border-bottom:double #000000 2.25pt;">&nbsp;</TD>
</TR>
</TABLE></DIV>
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 </DIV>
 <P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
underwriters have agreed to purchase all of the shares sold under the underwriting agreement if any of these shares are purchased. If an underwriter defaults, the underwriting
agreement provides that the purchase commitments of the nondefaulting underwriters may be increased or the underwriting agreement may be terminated. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We
have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended, or to contribute to payments the
underwriters may be required to make in respect of those liabilities. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
underwriters are offering the shares, subject to prior sale, when, as and if issued to and accepted by them, subject to approval of legal matters by their counsel, including the
validity of the shares, and other conditions contained in the underwriting agreement, such as the receipt by the underwriters of officer's certificates and legal opinions. The underwriters reserve the
right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Option to Purchase Additional Shares  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We have granted to the underwriters an option to purchase up to 1,125,000 additional shares at the same price per share as they are
paying for the shares shown in the table below. These additional shares would cover sales by the underwriters which exceed the total number of shares shown in the table above. The underwriters may
exercise this option at any time and from time to time, in whole or in part, within 30&nbsp;days after the date of this prospectus supplement. To the extent that the underwriters exercise this
option, each underwriter will purchase additional shares from us in approximately the same proportion as it purchased the shares shown in the table above. We will pay the expenses associated with the
exercise of this option. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Commissions and Discounts  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The underwriters have advised us that they propose initially to offer the shares to the public at the public offering price on the
cover page of this prospectus supplement and to dealers at that price less a concession not in excess of $0.594 per share. After the public offering, the public offering price and concession may be
changed. The following table shows the public offering price, underwriting discounts </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-11</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2><A
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<P style="font-family:times;"><FONT SIZE=2>and
commissions and proceeds before expenses to us. The information assumes either no exercise or full exercise by the underwriters of their option to purchase additional shares. </FONT></P>
 <DIV style="padding:0pt;position:relative;width:70%;margin-left:15%;">
<p style="font-family:times;"></FONT></P>

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<TD WIDTH="12pt" style="font-family:times;"></TD>
<TD WIDTH="6pt" ALIGN="RIGHT" style="font-family:times;"></TD>
<TD WIDTH="49pt" style="font-family:times;"></TD>
<TD WIDTH="12pt" style="font-family:times;"></TD>
<TD WIDTH="6pt" ALIGN="RIGHT" style="font-family:times;"></TD>
<TD WIDTH="77pt" style="font-family:times;"></TD>
<TD WIDTH="12pt" style="font-family:times;"></TD>
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<TH ALIGN="LEFT" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT><BR></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>Per Share </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>Without Option </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>With Option </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Initial price to public</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>24.75</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>185,625,000</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>213,468,750</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="White" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Underwriting discounts and commissions</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>0.99</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>7,425,000</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>8,538,750</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="TOP">
<TD VALIGN="BOTTOM" style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Proceeds, before expenses, to us</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>23.76</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>178,200,000</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT"  VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>$</FONT></TD>
<TD ALIGN="RIGHT" VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>204,930,000</FONT></TD>
<TD VALIGN="BOTTOM" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
</TABLE></DIV>
<!-- end of user-specified TAGGED TABLE -->
 </DIV>
 <P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
expenses of the offering, not including the underwriting discount, are estimated at $250,000 and are payable by us. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> No Sales of Similar Securities  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We have agreed that we will not offer, sell, contract to sell, pledge or otherwise dispose of, directly or indirectly, or file with
the Securities and Exchange Commission a registration statement under the Securities Act of 1933, as amended, relating to, any of our common shares of beneficial interest or securities convertible
into or exchangeable or exercisable for any of our common shares of beneficial interest, or publicly disclose the intention to make any offer, sale, pledge, disposition or filing, without the prior
written consent of the representatives for a period of 30&nbsp;days after the date of this prospectus supplement, except issuances of common shares of beneficial interest pursuant to the dividend
reinvestment component of our dividend reinvestment plan as in effect on the date hereof, the conversion or exchange of convertible or exchangeable securities or the exercise of
warrants or options, in each case outstanding on the date hereof, issuances pursuant to the exercise of employee stock options outstanding on the date hereof, or issuances of restricted securities
constituting either common or preferred units of our operating partnership in acquisition transactions. However, in the event that either (1)&nbsp;during the last 17&nbsp;days of the
"lock-up" period, we release earnings results or material news or a material event relating to us occurs or (2)&nbsp;prior to the expiration of the "lock-up" period, we
announce that we will release earnings results during the 16-day period beginning on the last day of the "lock-up" period, then in either case the expiration of the
"lock-up" will be extended until the expiration of the 18-day period beginning on the date of the release of the earnings results or the occurrence of the material news or
event, as applicable, unless the representatives waive, in writing, such an extension. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
executive officers and trustees have agreed that they will not offer, sell, contract to sell, pledge or otherwise dispose of, directly or indirectly, any of our common shares of
beneficial interest or securities convertible into or exchangeable or exercisable for any of our common shares of beneficial interest, enter into a transaction that would have the same effect, or
enter into any swap, hedge or other arrangement that transfers, in whole or in part, any of the economic consequences of ownership of our common shares of beneficial interest, whether any of these
transactions are to be settled by delivery of our common shares of beneficial interest or other securities, in cash or otherwise, or publicly disclose the intention to make any offer, sale, pledge or
disposition, or to enter into any transaction, swap, hedge or other arrangement, without, in each case, the prior written consent of the representatives for a period of 30&nbsp;days after the date
of this prospectus supplement, with certain exceptions. However, in the event that either (1)&nbsp;during the last 17&nbsp;days of the "lock-up" period, we release earnings results or
material news or a material event relating to us occurs or (2)&nbsp;prior to the expiration of the "lock-up" period, we announce that we will release earnings results during the
16-day period beginning on the last day of the "lock-up" period, then in either case the expiration of the "lock-up" will be extended until the expiration of the
18-day period beginning on the date of the release of the earnings results or the occurrence of the material news or event, as applicable, unless the representatives waive, in writing,
such an extension. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> New York Stock Exchange Listing  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The shares are listed on the New York Stock Exchange under the symbol "OFC." </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-12</FONT></P>

<HR NOSHADE>
<P style='font-family:times;page-break-before:always'></p>
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<P style="font-family:times;"><FONT SIZE=2><A
HREF="#bg11001a_main_toc">Table of Contents</A></FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Price Stabilization and Short Positions  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Until the distribution of the shares is completed, Securities and Exchange Commission rules may limit underwriters from bidding for
and purchasing our common shares. However, the underwriters may engage in transactions that stabilize the price of the common shares, such as bids or purchases to peg, fix or maintain that price. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
the underwriters create a short position in the common shares in connection with this offering, i.e.,&nbsp;if they sell more shares than are listed on the cover of this prospectus
supplement, the underwriters may reduce that short position by purchasing shares in the open market. The underwriters may also elect to reduce any short position by exercising all or part of the
underwriters' option to purchase additional shares described above. Purchases of our common shares to stabilize the price of our common shares or to reduce a short position may cause the price of our
common shares to be higher than it might be in the absence of such purchases. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Neither
we nor any of the underwriters makes any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price
of our common shares. In addition, neither we nor any of the underwriters makes any representation that the underwriters will engage in these transactions or that these transactions, once commenced,
will not be discontinued without notice. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Conflicts  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Wells Fargo Securities,&nbsp;LLC, J.P. Morgan Securities&nbsp;LLC, Barclays Capital&nbsp;Inc., certain of the other underwriters
and their affiliates have provided investment banking, commercial banking and financial advisory services for us from time to time for which they have received customary fees and expenses. Wells Fargo
Securities,&nbsp;LLC, J.P. Morgan Securities&nbsp;LLC, Barclays Capital&nbsp;Inc., certain of the other underwriters and their affiliates may, from time to time, engage in other transactions
with us and perform other services for us in the ordinary course of their businesses. In particular, affiliates of Wells Fargo Securities,&nbsp;LLC, J.P. Morgan Securities&nbsp;LLC, Barclays
Capital&nbsp;Inc., KeyBanc Capital Markets&nbsp;Inc., RBC Capital Markets,&nbsp;LLC, Comerica Securities,&nbsp;Inc., PNC Capital Markets&nbsp;LLC and SunTrust Robinson Humphrey,&nbsp;Inc.
are lenders under our unsecured revolving credit facility. As described under "Use of Proceeds," we intend to use net proceeds from this offering to repay borrowings outstanding under our unsecured
revolving credit facility. Because affiliates of Wells Fargo Securities,&nbsp;LLC, J.P. Morgan Securities&nbsp;LLC, Barclays Capital&nbsp;Inc., KeyBanc Capital Markets&nbsp;Inc., RBC Capital
Markets,&nbsp;LLC, Comerica Securities,&nbsp;Inc., PNC Capital Markets&nbsp;LLC and SunTrust Robinson Humphrey,&nbsp;Inc. are lenders under our unsecured revolving credit facility, those
affiliates will receive a portion of the net proceeds from this offering through the repayment of those borrowings. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Other Relationships  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In the ordinary course of their various business activities, the underwriters and their respective affiliates may make or hold a broad
array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of
their customers and such investment and securities activities may involve securities and/or instruments of ours. The underwriters and their respective affiliates may also make investment
recommendations and/or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short
positions in such securities and instruments. In addition, affiliates of Wells Fargo Securities,&nbsp;LLC are currently collectively one of the largest tenants in our portfolio, by percentage of
annualized rental revenue. Additionally, on August&nbsp;3, 2012, we entered into a $200&nbsp;million unsecured term loan agreement with a group of lenders for which Wells Fargo
Securities,&nbsp;LLC, an underwriter of this offering, acted as sole arranger and sole book runner, Wells Fargo Bank, National Association acted as administrative agent and Capital One, N.A. acted
as documentation agent. Affiliates of KeyBanc Capital Markets&nbsp;Inc. and PNC Capital Markets&nbsp;LLC are also lenders under the term loan. We borrowed </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-13</FONT></P>

<HR NOSHADE>
<P style='font-family:times;page-break-before:always'></p>
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<P style="font-family:times;"><FONT SIZE=2><A
HREF="#bg11001a_main_toc">Table of Contents</A></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>$120&nbsp;million
under the term loan, with a right for us to borrow an additional $80&nbsp;million provided that there is no default under the agreement. The term loan matures on August&nbsp;2,
2019. The variable interest rate on the loan is based on the LIBOR rate (customarily the 30-day rate) plus 2.10% to 2.60%, as determined by our leverage levels. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Sales Outside the United States  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;No action has been taken in any jurisdiction (except in the United States) that would permit a public offering of the securities, or
the possession, circulation or distribution of this prospectus supplement, the accompanying prospectus or any other material relating to us or the securities in any jurisdiction where action for that
purpose is required. Accordingly, the securities may not be offered or sold, directly or indirectly, and none of this prospectus supplement, the accompanying prospectus or any other offering material
or advertisements in connection with the securities may be distributed or published, in or from any country or jurisdiction except in compliance with any applicable rules and regulations of any such
country or jurisdiction. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Each
of the underwriters may arrange to sell securities offered hereby in certain jurisdictions outside the United States, either directly or through affiliates, where they are
permitted to do so. In that regard, Wells Fargo Securities,&nbsp;LLC may arrange to sell securities in certain jurisdictions through an affiliate, Wells Fargo Securities International Limited, or
WFSIL. WFSIL is a wholly-owned indirect subsidiary of Wells Fargo&nbsp;&amp; Company and an affiliate of Wells Fargo Securities,&nbsp;LLC. WFSIL is a U.K. incorporated investment firm regulated by the
Financial Services Authority. Wells Fargo Securities is the trade name for certain corporate and investment banking services of Wells Fargo&nbsp;&amp; Company and its affiliates, including Wells Fargo
Securities,&nbsp;LLC and WFSIL. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Notice to Prospective Investors in the European Economic Area  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In relation to each Member State of the European Economic Area which has implemented the Prospectus Directive (each, a "Relevant
Member State"), including each Relevant Member State that has implemented amendments to Article&nbsp;3(2) of the Prospectus Directive introduced by the 2010 PD Amending Directive (each, an "Early
Implementing Member State"), an offer of common shares to the public may not be made in that Relevant Member State and each underwriter represents and agrees that with effect from and including the
date on which the Prospectus Directive is implemented in that Relevant Member State (the "Relevant Implementation Date") it has not made and will not make an offer of common shares which are the
subject of the offering contemplated by this prospectus supplement and the accompanying prospectus to the public in that Relevant Member State prior to the publication of a prospectus in relation to
common shares which has been approved by the competent authority in that Relevant Member State or, where appropriate, approved in another Relevant Member State and notified to the competent authority
in that Relevant Member State, all in accordance with the Prospectus Directive, except that an offer of common shares which are the subject of the offering contemplated by this prospectus supplement
and the accompanying prospectus to the public in that Relevant Member State may be made at any time under the following exemptions under the Prospectus Directive, if they have been implemented in that
Relevant Member State: </FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(a)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>to
any legal entity which is a "qualified investor" as defined in the Prospectus Directive;
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(b)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>to
fewer than 100 (or, in the case of Early Implementing Member States, 150) natural or legal persons (other than "qualified investors" as defined in the
Prospectus Directive) subject to obtaining the prior consent of the representatives; or
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(c)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>in
any other circumstances falling within Article&nbsp;3(2) of the Prospectus Directive, </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>provided
that no such offer of common shares referred to in (a)&nbsp;to (c)&nbsp;above shall require the issuer or any underwriter to publish a prospectus pursuant to Article&nbsp;3 of the
Prospectus Directive or supplement a prospectus pursuant to Article&nbsp;16 of the Prospectus Directive and each person who initially acquires any common shares or to whom any offer is made will be
deemed to have represented, warranted and </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-14</FONT></P>

<HR NOSHADE>
<P style='font-family:times;page-break-before:always'></p>
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<P style="font-family:times;"><FONT SIZE=2><A
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<P style="font-family:times;"><FONT SIZE=2>agreed
to and with the Company or any underwriter that it is a qualified investor within the meaning of the law in that Relevant Member State implementing Article&nbsp;2(1)(e) of the Prospectus
Directive. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;For
the purposes of this provision, the expression an "offer to the public" in relation to any common shares in any Relevant Member State means the communication in any form and by any
means of sufficient information on the terms of the offer and the common shares to be offered so as to enable an investor to decide to purchase or subscribe to the common shares, as the same may be
varied in that Relevant Member State by any measure implementing the Prospectus Directive in that Relevant Member State and the expression "Prospectus Directive" means Directive 2003/71/EC of the
European Parliament and of the Council of 4&nbsp;November 2003 (and amendments thereto, including the 2010 PD Amending Directive, to the extent implemented in the Relevant Member State), and
includes any relevant implementing measure in the Relevant Member State. The expression "2010 PD Amending Directive" means Directive 2010/73/EU. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Notice to Prospective Investors in the United Kingdom  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This prospectus supplement and the accompanying prospectus and any other material in relation to the common shares described herein
and therein are only being distributed to, and are only directed at, persons in the United Kingdom that are qualified investors within the meaning of Article&nbsp;2(1)(e) of the Prospective
Directive that also (i)&nbsp;have professional experience in matters relating to investments falling within Article&nbsp;19(5) of the Financial Services and Markets Act 2000 (Financial Promotion)
Order 2005, as amended, (the "Order"), (ii)&nbsp;fall within Article&nbsp;49(2)(a) to (d)&nbsp;of the Order and (iii)&nbsp;are persons to whom it may otherwise lawfully be communicated (all
such persons together being referred to as "relevant persons"). The common shares are only available to, and any invitation, offer or agreement to engage in investment activity with respect to such
common shares will be engaged in only with, relevant persons. This prospectus supplement and the accompanying prospectus and their contents are confidential and should not be distributed, published or
reproduced (in whole or in part) or disclosed by recipients to any other person in the United Kingdom. Any person in the United Kingdom that is not a relevant person should not act or rely on this
prospectus supplement or the accompanying prospectus or any of their contents. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
distribution of this prospectus supplement and the accompanying prospectus in the United Kingdom to anyone not falling within the above categories is not permitted and may
contravene FSMA. No person falling outside those categories should treat this prospectus supplement and the accompanying prospectus as constituting a promotion to him, or act on it for any purposes
whatever. Recipients of this prospectus supplement and the accompanying prospectus are advised that we, the underwriters and any other person that communicates this prospectus supplement and the
accompanying prospectus are not, as a result solely of communicating this prospectus supplement and the accompanying prospectus, acting for or advising them and are not responsible for providing
recipients of this prospectus supplement and the accompanying prospectus with the protections which would be given to those who are clients of any aforementioned entities that is subject to the
Financial Services Authority Rules. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Notice to Prospective Investors in France  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Each of the Company and the underwriters has not offered or sold and will not offer or sell, directly or indirectly, common shares to
the public in France, and has not distributed or caused to be distributed and will not distribute or cause to be distributed to the public in France, this prospectus supplement and the accompanying
prospectus or any other offering material relating to the common shares. Offers, sales and distributions that have been and will be made in France have been and will be made only to
(a)&nbsp;providers of the investment service of portfolio management for the account of third parties, and (b)&nbsp;qualified investors (</FONT><FONT SIZE=2><I>investisseurs
qualifi&eacute;s</I></FONT><FONT SIZE=2>), other than individuals, all as defined in, and in accordance with, Articles&nbsp;L. 411-1, L. 411-2, and D.
411-1 of the French Code mon&eacute;taire et financier. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-15</FONT></P>

<HR NOSHADE>
<P style='font-family:times;page-break-before:always'></p>
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<P style="font-family:times;"><FONT SIZE=2><A
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<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
common shares may be resold directly or indirectly only in compliance with Article&nbsp;L. 411-1, L.&nbsp;411-2, L.&nbsp;412-1 and
L.&nbsp;621-8 to L.&nbsp;621-8-3 of the French Code </FONT><FONT SIZE=2><I>mon&eacute;taire et financier</I></FONT><FONT SIZE=2>. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Neither
this prospectus supplement nor the accompanying prospectus prepared in connection with the common shares nor any other offering material relating to the common shares has been
submitted to the clearance procedures of the </FONT><FONT SIZE=2><I>Autorit&eacute; des march&eacute;s financiers</I></FONT><FONT SIZE=2> or notified to the </FONT> <FONT SIZE=2><I>Autorit&eacute; des march&eacute;s financiers</I></FONT><FONT SIZE=2>
by the competent authority of another member state of the European Economic Area.
 </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Notice to Prospective Investors in Germany  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The common shares offered by this prospectus supplement and the accompanying prospectus have not been and will not be offered to the
public within the meaning of the German Securities Prospectus Act (</FONT><FONT SIZE=2><I>Wertpapierprospektgesetz</I></FONT><FONT SIZE=2>). No securities prospectus pursuant to the German Securities
Prospectus Act has been or will be published or circulated in Germany or filed with the German Federal Financial Supervisory Authority (</FONT><FONT SIZE=2><I>Bundesanstalt f&uuml;r
Finanzdienstleistungsaufsicht</I></FONT><FONT SIZE=2>). This prospectus supplement and the accompanying prospectus does not constitute an offer to the public in Germany, and it does not serve for
public distribution of the common shares in Germany. Neither this prospectus supplement nor the accompanying prospectus, nor any other document issued in connection with this offering, may be issued
or distributed to any person in Germany except under circumstances that do not constitute an offer to the public under the German Securities Prospectus Act. Prospective Investors should consult with
their legal and/or tax advisor before investing into the common shares. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Notice to Prospective Investors in Italy  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The offering of the common shares has not been registered pursuant to Italian securities legislation and, accordingly, no common
shares may be offered, sold or delivered, nor may copies of this prospectus supplement and the accompanying prospectus or of any other document relating to the common shares be distributed in the
Republic of Italy, except: </FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(i)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>to
qualified investors (</FONT><FONT SIZE=2><I>investitori qualificati</I></FONT><FONT SIZE=2>), as defined pursuant to Article&nbsp;100 of Legislative
Decree No.&nbsp;58 of 24&nbsp;February 1998, as amended (the Financial Services Act) and Article&nbsp;34-</FONT><FONT SIZE=2><I>ter</I></FONT><FONT SIZE=2>, first paragraph, letter
b)&nbsp;of CONSOB Regulation No.&nbsp;11971 of 14&nbsp;May 1999, as amended from time to time (Regulation No.&nbsp;11971); or
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(ii)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>in
other circumstances which are exempted from the rules on public offerings pursuant to Article&nbsp;100 of the Financial Services Act and
Article&nbsp;34-</FONT><FONT SIZE=2><I>ter</I></FONT><FONT SIZE=2> of Regulation No.&nbsp;11971. </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Any
offer, sale or delivery of the common shares or distribution of copies of this prospectus supplement and the accompanying prospectus or any other document relating to the common
shares in the Republic of Italy under (i)&nbsp;or (ii)&nbsp;above must be: </FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(a)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>made
by an investment firm, bank or financial intermediary permitted to conduct such activities in the Republic of Italy in accordance with the Financial
Services Act, CONSOB Regulation No.&nbsp;16190 of 29&nbsp;October 2007 (as amended from time to time) and Legislative Decree No.&nbsp;385 of 1&nbsp;September 1993, as amended (the Banking
Act); and
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(b)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>in
compliance with Article&nbsp;129 of the Banking Act, as amended, and the implementing guidelines of the Bank of Italy, as amended from time to time,
pursuant to which the Bank of Italy may request information on the issue or the offer of the common shares in the Republic of Italy; and
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>(c)</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>in
compliance with any other applicable laws and regulations or requirement imposed by CONSOB or other Italian authority. </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Please
note that in accordance with Article&nbsp;100-</FONT><FONT SIZE=2><I>bis</I></FONT><FONT SIZE=2> of the Financial Services Act, where no exemption from the rules
on public offerings applies under (i)&nbsp;and (ii)&nbsp;above, the subsequent distribution of the common shares on the secondary market in Italy must be made in compliance with the public offer
and the prospectus requirement rules provided under the Financial Services Act and </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-16</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>Regulation
No.&nbsp;11971. Failure to comply with such rules may result in the sale of such common shares being declared null and void and in the liability of the intermediary transferring the
common shares for any damages suffered by the investors. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Notice to Prospective Investors in Switzerland  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Company has not been authorized by the Swiss Financial Market Supervision Authority as a foreign investment fund for public
distribution in Switzerland pursuant to article&nbsp;120 of the Swiss Federal Act on Collective investment Schemes of June&nbsp;23, 2006 ("CISA"). Accordingly, the common shares may not be offered
or distributed to the public in or from Switzerland and neither this prospectus supplement and the accompanying prospectus nor any other offering
material relating to the common shares may be distributed in connection with any such offering or distribution. The common shares may only be offered and this prospectus supplement and the
accompanying prospectus may only be distributed in or from Switzerland to qualified investors (as defined under article&nbsp;10 para. 3 of the CISA). </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-17</FONT></P>

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<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> <A NAME="Legal"></A>LEGAL MATTERS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Certain legal matters in connection with the common shares offered hereby will be passed upon for us by Morgan,
Lewis&nbsp;&amp; Bockius&nbsp;LLP, Philadelphia, Pennsylvania and Saul Ewing&nbsp;LLP, Baltimore, Maryland and for the underwriters by Clifford Chance US&nbsp;LLP, New York, New York. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> <A NAME="INFO"></A>WHERE YOU CAN FIND MORE INFORMATION  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We have filed a registration statement on Form&nbsp;S-3 with the Securities and Exchange Commission in
connection with this offering. In addition, we file annual, quarterly, and current reports, proxy statements and other information with the Securities and Exchange Commission. You may read and copy
the registration statement and any other documents filed by us at the Securities and Exchange Commission's Public Reference Room at 100&nbsp;F Street, N.E., Washington, D.C. 20549. Our Securities
and Exchange Commission filings are also available to the public at the Securities and Exchange Commission's Internet site at </FONT><FONT SIZE=2><I>http://www.sec.gov</I></FONT><FONT SIZE=2>. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This
prospectus supplement and the accompanying prospectus do not contain all of the information included in the registration statement. If a reference is made in this prospectus
supplement or the accompanying prospectus to any of our contracts or other documents, the reference may not be complete and you should refer to the exhibits that are a part of or incorporated by
reference in the registration statement for a copy of the contract or document. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
Securities and Exchange Commission allows us to "incorporate by reference" into this prospectus supplement the information we file with the Securities and Exchange Commission, which
means that we can disclose important information to you by referring you to those documents. Information incorporated by reference is part of this prospectus supplement. Later information filed with
the Securities and Exchange Commission will update and supersede this information. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We
incorporate by reference the documents listed below and any future filings we make with the Securities and Exchange Commission under Sections&nbsp;13(a), 13(c), 14 or 15(d) of the
Exchange Act until this offering is completed:</FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our Annual Report on Form&nbsp;10-K for the year ended December&nbsp;31, 2011, although the financial
statements, Selected Financial Data and Management's Discussion and Analysis of Financial Condition and Results of Operations contained therein were not revised for the reclassification of properties
newly-classified as discontinued operations in the Quarterly Reports on Form&nbsp;10-Q for the quarters ended March&nbsp;31, 2012 (as amended) and June&nbsp;30, 2012; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our Quarterly Reports on Form&nbsp;10-Q for the quarters ended March&nbsp;31, 2012 (as amended) and
June&nbsp;30, 2012, although the financial statements and Management's Discussion and Analysis of Financial Condition and Results of Operations contained in our Quarterly Report on
Form&nbsp;10-Q for the quarter ended March&nbsp;31, 2012 (as amended) were not revised for the reclassification of properties newly-classified as discontinued operations in the
Quarterly Report on Form&nbsp;10-Q for the quarter ended June&nbsp;30, 2012; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our Definitive Proxy Statement for the 2012 Annual Meeting of Shareholders, filed with the Securities and Exchange
Commission on March&nbsp;29, 2012; and </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our Current Reports on Form&nbsp;8-K filed with the Securities and Exchange Commission on
February&nbsp;16, 2012, March&nbsp;9, 2012, May&nbsp;15, 2012, June&nbsp;19, 2012, June&nbsp;26, 2012, June&nbsp;27, 2012, September&nbsp;28, 2012 (Items&nbsp;2.05 and 2.06) and
October&nbsp;10, 2012. </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;You
may request a copy of these filings, at no cost, by contacting Stephanie&nbsp;M. Krewson, Vice President of Investor Relations, Corporate Office Properties Trust,
6711&nbsp;Columbia Gateway, Suite&nbsp;300, Columbia, Maryland 21046, by telephone at 443-285-5400, by facsimile at
443-285-7650, by e-mail at </FONT><FONT SIZE=2><I>ir@copt.com</I></FONT><FONT SIZE=2> or by visiting our website, </FONT> <FONT SIZE=2><I>www.copt.com</I></FONT><FONT SIZE=2>. The information contained on our website is not part of this prospectus
supplement. Our reference to our website is intended to be an
inactive textual reference only. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>S-18</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2><B> PROSPECTUS  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B>
<IMG SRC="g694461.jpg" ALT="LOGO" WIDTH="226" HEIGHT="130">
  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=5><B>CORPORATE OFFICE PROPERTIES TRUST  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B>COMMON SHARES OF BENEFICIAL INTEREST<BR>
PREFERRED SHARES OF BENEFICIAL INTEREST<BR>
DEPOSITARY SHARES<BR>
WARRANTS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This prospectus relates to common shares of beneficial interest, preferred shares of beneficial interest, depositary shares representing interests
in preferred shares and warrants to purchase common shares and/or preferred shares, or any combination of these securities, that we may sell from time to time in one or more offerings. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This
prospectus describes some of the general terms that may apply to these securities. We will provide the specific terms and conditions of these sales and the securities offered in
supplements to this prospectus prepared in connection with each offering. The prospectus supplement may also add, update or change information contained in this prospectus. You should read this
prospectus and each applicable prospectus supplement carefully before you invest in the securities. The securities may be offered directly, through agents on our behalf to or through underwriters. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
common shares are listed on the New York Stock Exchange under the symbol "OFC." We have not yet determined whether any of the other securities that may be offered by this prospectus
will be listed on any exchange, inter-dealer quotation system, or over-the-counter market. If we decide to seek listing of any such securities, a prospectus supplement relating
to those securities will disclose the exchange, quotation system or market on which the securities will be listed. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><I>

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<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT><FONT
SIZE=3><B>You should carefully read and consider the risk factors included in our periodic reports and other information that we file with the Securities
and Exchange Commission before you invest in the securities described in this prospectus.</B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><I>

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<BR></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Neither
the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or
complete. Any representation to the contrary is a criminal offense. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><I>

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<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>The
date of this prospectus is March&nbsp;29, 2012. </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>
<A NAME="BG11002_TOC"></A> </FONT></P>
 <DIV style="padding:0pt;position:relative;width:80%;margin-left:10%;">
<p style="font-family:times;"></FONT></P>

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<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Abt"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>ABOUT THIS PROSPECTUS</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Abt"><FONT SIZE=2>3</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#For"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>FORWARD-LOOKING STATEMENTS</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#For"><FONT SIZE=2>3</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#cc11002_summary"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>SUMMARY</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#cc11002_summary"><FONT SIZE=2>5</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#cc11002_our_company"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>OUR COMPANY</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#cc11002_our_company"><FONT SIZE=2>5</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Use"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>USE OF PROCEEDS</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Use"><FONT SIZE=2>6</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Ratios"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>RATIOS OF EARNINGS TO COMBINED FIXED CHARGES AND PREFERRED SHARE DIVIDENDS</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Ratios"><FONT SIZE=2>6</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Desp_shares"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>DESCRIPTION OF SHARES</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Desp_shares"><FONT SIZE=2>6</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Desp_Warr"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>DESCRIPTION OF WARRANTS</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Desp_Warr"><FONT SIZE=2>18</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Federal"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>FEDERAL INCOME TAX MATTERS</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Federal"><FONT SIZE=2>19</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Plan"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>PLAN OF DISTRIBUTION</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Plan"><FONT SIZE=2>32</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Expert"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>EXPERTS</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Expert"><FONT SIZE=2>33</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Sell_sec"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>SELLING SECURITYHOLDERS</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Sell_sec"><FONT SIZE=2>33</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
</TR>
<TR VALIGN="BOTTOM">
<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Leg_Mtr"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>LEGAL MATTERS</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Leg_Mtr"><FONT SIZE=2>34</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
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<TD VALIGN="TOP" style="font-family:times;"><A HREF="#Where"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>WHERE YOU CAN FIND MORE INFORMATION</FONT></A></TD>
<TD VALIGN="TOP" style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><A HREF="#Where"><FONT SIZE=2>34</FONT></A></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
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 <P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT><FONT
SIZE=2><I>The terms "COPT," "Company," "we," "our" and "us" refer to Corporate Office Properties Trust, individually or together with its subsidiaries, including Corporate
Office Properties,&nbsp;L.P., which we refer to as our operating partnership, and our predecessors, unless the context suggests otherwise. The term "you" refers to a prospective
investor.</I></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>2</FONT></P>

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<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Abt"></A>ABOUT THIS PROSPECTUS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission, or SEC, using a "shelf"
registration process, which enables us, from time to time, to offer and sell in one or more offerings common shares, preferred shares, depositary shares and warrants to purchase common shares and/or
preferred shares or any combination of these securities. This prospectus contains a general description of the securities that we may offer. Each time we sell any securities pursuant to this
prospectus, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement also may add, update or change information
contained in this prospectus. You should read this prospectus and the applicable prospectus supplement, together with the additional information described below under the heading "Where You Can Find
More Information," before you decide whether to invest in the securities. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="For"></A>FORWARD-LOOKING STATEMENTS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This section contains "forward-looking" statements, as defined in the Private Securities Litigation Reform Act of 1995, that are based
on our current expectations, estimates and projections about future events and financial trends affecting the financial condition and operations of our business. Forward-looking statements can be
identified by the use of words such as "may," "will," "should," "could," "believe," "anticipate," "expect," "estimate," "plan" or other comparable terminology. Forward- looking statements are
inherently subject to risks and uncertainties, many of which we cannot predict with accuracy and some of which we might not even anticipate. Although we believe that the expectations, estimates and
projections reflected in such forward-looking statements are based on reasonable assumptions at the time made, we can give no assurance that these expectations, estimates and projections will be
achieved. Future events and actual results may differ materially from those discussed in the forward-looking statements. Important factors that may affect these expectations, estimates and projections
include, but are not limited to:</FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>general economic and business conditions, which will, among other things, affect office property and data center demand
and rents, tenant creditworthiness, interest rates, financing availability and property values; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>adverse changes in the real estate markets, including, among other things, increased competition with other companies; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>governmental actions and initiatives, including risks associated with the impact of a government shutdown and budgetary
reductions or impasses, such as a reduction in rental revenues, non-renewal of leases and/or a curtailment of demand for additional space by our strategic customers; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our ability to sell properties included in our Strategic Reallocation Plan; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our ability to borrow on favorable terms; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>risks of real estate acquisition and development activities, including, among other things, risks that development
projects may not be completed on schedule, that tenants may not take occupancy or pay rent or that development and operating costs may be greater than anticipated; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>risks of investing through joint venture structures, including risks that our joint venture partners may not fulfill their
financial obligations as investors or may take actions that are inconsistent with our objectives; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>changes in our plans for properties or views of market economic conditions or failure to obtain development rights, either
of which could result in recognition of impairment losses; </FONT></DD></DL>
</UL>
<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>3</FONT></P>

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<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>our ability to satisfy and operate effectively under Federal income tax rules relating to real estate investment trusts
and partnerships; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the dilutive effects of issuing additional common shares; and </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>environmental requirements. </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We
undertake no obligation to update or supplement forward-looking statements. For further information on factors that could affect the Company and the statements contained herein, you
should refer to the "Risk Factors" section in our most recent Annual Report on Form&nbsp;10-K filed with the Securities and Exchange Commission, as it may be updated by information
included in our Quarterly Reports on Form&nbsp;10-Q filed with the Securities and Exchange Commission. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>4</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<BR></FONT></P>


<P style="font-family:times;"><FONT SIZE=2><I> </i></font></p>
<DIV style="width:100%;border:#000000 solid 1pt;padding-top:12pt;padding-right:12pt;padding-bottom:1pt;padding-left:12pt;">
 <P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="cc11002_summary"> </A>
<A NAME="toc_cc11002_1"> </A>
<BR></FONT><FONT SIZE=2><B>  <A NAME="Sum"></A>SUMMARY    <BR>    </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT><FONT SIZE=2><B><I>This prospectus summary calls your attention to selected information in this document, but it does not contain
all the information that is important to you. To understand us and the securities that may be offered through this prospectus, you should read this entire prospectus carefully, including the "Risk
Factors" and other information included in the documents to which we refer you in the section called "Where You Can Find More Information" in this prospectus.</I></B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><A
NAME="cc11002_our_company"> </A>
<A NAME="toc_cc11002_2"> </A>
<BR></FONT><FONT SIZE=2><B>  <A NAME="Our"></A>OUR COMPANY    <BR>    </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;General.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;We are an office real estate investment trust, or REIT, that focuses primarily on serving the specialized requirements of
strategic
customers in the United States Government and defense information technology sectors. We acquire, develop, manage and lease office and data center properties that are typically concentrated in large
office parks primarily located adjacent to government demand drivers and/or in office markets that we believe possess growth opportunities. As of December&nbsp;31, 2011, our investments in real
estate included the following:</FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>238 operating office properties totaling 20.5&nbsp;million square feet that were 86% occupied; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>seven office properties under construction or redevelopment that we estimate will total approximately 903,000 square feet
upon completion, including one partially operational property included above; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>land held or under pre-construction totaling 2,330 acres (including 583 acres controlled but not owned) that
we believe are potentially developable into approximately 20.6&nbsp;million square feet; and </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>a partially operational, wholesale data center which upon completion and stabilization is expected to have a critical load
of 18 megawatts. </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We
conduct almost all of our operations through our operating partnership, Corporate Office Properties,&nbsp;L.P., a Delaware limited partnership, of which we are the managing general
partner. The Operating Partnership owns real estate both directly and through subsidiary partnerships and limited liability companies. The Operating Partnership also owns 100% of a number of entities
that provide real estate services such as property management and construction and development services primarily for our properties, but also for third parties. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Interests
in our Operating Partnership are in the form of common and preferred units. As of December&nbsp;31, 2011, we owned 94.4% of the outstanding common units and 95.8% of the
outstanding preferred units in our Operating Partnership. The remaining common and preferred units in our Operating Partnership were owned by third parties, which included certain of our Trustees. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We
believe that we are organized and have operated in a manner that permits us to satisfy the requirements for taxation as a REIT under the Internal Revenue Code of 1986, as amended, and
we intend to continue to operate in such a manner. Provided we continue to qualify for taxation as a REIT, we generally will not be subject to Federal income tax on our taxable income that is
distributed to our shareholders. A REIT is subject to a number of organizational and operational requirements, including a requirement that it distribute to its shareholders at least 90% of its annual
taxable income (excluding net capital gains). </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
executive offices are located at 6711 Columbia Gateway Drive, Suite&nbsp;300, Columbia, Maryland&nbsp;21046 and our telephone number is (443)&nbsp;285-5400. </FONT></P>
 <p style="font-family:times;"><font style="font-size:1pt;line-height:1pt;">&nbsp;</font></p>
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 <P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>5</FONT></P>

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<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Use"></A>USE OF PROCEEDS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Unless otherwise set forth in a prospectus supplement accompanying this prospectus, we intend to use the net proceeds of any sale of
the securities that we may offer under this prospectus and any accompanying prospectus supplement for working capital and other general business purposes, which may include capital expenditures,
acquisition or development of additional properties, repayment of indebtedness and repurchases of outstanding shares. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Ratios"></A>RATIOS OF EARNINGS TO COMBINED FIXED CHARGES<BR>
AND PREFERRED SHARE DIVIDENDS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The following table sets forth our ratios of earnings to combined fixed charges and preferred share dividends for each of the last five
calendar years. For purposes of calculating the ratio of earnings to combined fixed charges and preferred share dividends, (loss) earnings were computed by adding fixed charges (excluding preferred
share dividends, preferred unit distributions, capitalized interest, gain on sales of real estate, amortization of capitalized interest and
distributed loss of equity investees to (loss) income from continuing operations before equity in (loss) income of unconsolidated entities and income taxes. Fixed charges consist of interest costs,
capitalized amortization of debt issuance costs, dividends to preferred shareholders and distributions to preferred unit holders. This information is given on a historical basis. </FONT></P>
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<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>2011 </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>2010 </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>2009 </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>2008 </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
<TH COLSPAN=2 ALIGN="CENTER" style="font-family:times;border-bottom:solid #000000 1.0pt;"><FONT SIZE=1><B>2007 </B></FONT></TH>
<TH style="font-family:times;"><FONT SIZE=1>&nbsp;</FONT></TH>
</TR>
<TR BGCOLOR="#CCEEFF" VALIGN="BOTTOM">
<TD style="font-family:times;"><p style="font-family:times;margin-left:10pt;text-indent:-10pt;"><FONT SIZE=2> </FONT><FONT SIZE=2>Ratio of (loss) earnings to combined fixed charges and preferred share dividends</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>*</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>1.05x</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>1.21x</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>1.18x</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD ALIGN="RIGHT" style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;</FONT></TD>
<TD style="font-family:times;"><FONT SIZE=2>**</FONT></TD>
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<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>*</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>Combined
fixed charges and preferred share dividends exceeded total (loss) earnings by $152.9&nbsp;million.
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>**</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>Combined
fixed charges and preferred share dividends exceeded total (loss) earnings by $4.9&nbsp;million. </FONT></DD></DL>
 </DIV>
 <P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Desp_shares"></A>DESCRIPTION OF SHARES  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT><FONT SIZE=2><I>The following summary of the terms and provisions of our common shares, preferred shares and depositary shares
representing interests in preferred shares does not purport to be complete and is subject to and qualified in its entirety by reference to our Declaration of Trust and the Articles Supplementary to
our Declaration of Trust relating to the designation of each series of our preferred shares, each of which is available from us as described in "Where You Can Find More
Information."</I></FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> General  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Under our Declaration of Trust, we are authorized to issue up to 125,000,000 common shares and 15,000,000 preferred shares. As of
December&nbsp;31, 2008, 2,200,000 shares were classified as 8.0% Series&nbsp;G Cumulative Redeemable Preferred Shares, all of which were issued and outstanding; 2,000,000 shares were classified as
7.5% Series&nbsp;H Cumulative Redeemable Preferred Shares, all of which were issued and outstanding; 3,390,000 shares were classified as 7.625% Series&nbsp;J Cumulative Redeemable Preferred
Shares, all of which were issued and outstanding; and 600,000 shares were classified as 5.60% Series&nbsp;K Cumulative Redeemable Preferred Shares, 531,667 of which were issued and outstanding; Our
Board of Trustees may increase the authorized number of common shares and preferred shares without shareholder approval. As of December&nbsp;31, 2011, there were 72,011,324 common shares issued and
outstanding. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We
are authorized to issue preferred shares in one or more classes or subclasses, with the designations, preferences, conversion and other rights, voting powers, restrictions,
limitations as to </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>6</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>dividends,
qualifications and terms and conditions of redemption, in each case, as are permitted by Maryland law and as our Board of Trustees may determine by resolution. Except for the
Series&nbsp;G Preferred Shares, the Series&nbsp;H Preferred Shares, the Series&nbsp;J Preferred Shares and the Series&nbsp;K Preferred Shares, there are currently no other classes or series of
preferred shares authorized. However, our Operating Partnership has issued to a third party 352,000 Series&nbsp;I Preferred Units. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;As
of December&nbsp;31, 2011, we owned approximately 94% of the outstanding common units and 2,200,000 Series&nbsp;G Preferred Units, 2,000,000 Series&nbsp;H Preferred Units,
3,390,000 Series&nbsp;J Preferred Units and 531,667 Series&nbsp;K Preferred Units issued by our Operating Partnership. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Each
series of units has economic terms substantially equivalent to the economic terms of the corresponding Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K
Preferred Shares, respectively, that we have issued. The 352,000 Series&nbsp;I Preferred Units of our Operating Partnership are owned by a third party and have a liquidation preference of $25.00 per
unit. Prior to the distributions with respect to common units of our Operating Partnership, and through September&nbsp;23, 2019, each Series&nbsp;I Preferred Unit is entitled to a priority
distribution of 7.5% of the liquidation value per Series&nbsp;I Preferred Unit, payable quarterly. After September&nbsp;23, 2019, the priority distribution on the Series&nbsp;I Preferred Units
increases in accordance with the terms thereof. Each Series&nbsp;I Preferred Unit is convertible into 0.5 common units at any time at the option of the holder. We may redeem the Series&nbsp;I
Preferred Units at any time after September&nbsp;23, 2019 for any amount equal to their liquidation preference. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
economic terms of the common units will be substantially equivalent to the economic terms of the common shares. The Series&nbsp;G, Series&nbsp;H, Series&nbsp;I, Series&nbsp;J
and Series&nbsp;K Preferred Units are treated equally (i.e.,&nbsp;are </FONT><FONT SIZE=2><I>pari passu</I></FONT><FONT SIZE=2>) in priority over the common units in our Operating Partnership
with respect to liquidation payments and quarterly distributions. Distributions on these preferred units are the source of funds for the payment of dividends on our preferred shares. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Except
in certain limited circumstances, at any time that we hold less than 90% of the outstanding partnership units in our Operating Partnership, any amendment to the Operating
Partnership agreement must be approved by the vote of a majority of the common and preferred units not held by us, each voting as a separate class. If we were to hold 90% or more of the outstanding
partnership units, we would have the right to amend the Operating Partnership agreement without first seeking such unitholder approval. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2><B> Common Shares  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;All common shares that are currently outstanding have been, or when issued upon redemption of common and preferred units of our
Operating Partnership in accordance with the terms of the Operating Partnership agreement will be, duly authorized, fully paid and nonassessable. Subject to the preferential rights of our
Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares, as well as any other shares or series of beneficial interest that we may issue in the future, and to the
provisions of our Declaration of Trust regarding the restriction on transfer of common shares, holders of common shares are entitled to receive dividends on such shares if, as and when authorized and
declared by the Board of Trustees out of assets legally available therefor and to share ratably in our assets legally available for distribution to our shareholders in the event of the liquidation,
dissolution or winding-up of COPT after payment of, or adequate provision for, all of our known debts and liabilities. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Subject
to the provisions of our Declaration of Trust regarding restrictions on transfer of shares of beneficial interest, each outstanding common share entitles the holder thereof to
one vote on all matters submitted to a vote of shareholders, including the election of Trustees, and, except as provided with respect to any other class or series of shares of beneficial interest, the
holders of such common shares possess the exclusive voting power. There is no cumulative voting in the election of Trustees, which means that the holders of a majority of the outstanding common shares
can elect all of the Trustees then standing for election. The Declaration of Trust provides for the election of Trustees to </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>7</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>staggered
three-year terms. See the section below entitled "Classification of Board, Vacancies and Removal of Trustees." </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Holders
of common shares have no preference, conversion, sinking fund, redemption or appraisal rights and have no preemptive rights to subscribe for any of our securities. Subject to the
provisions of the Declaration of Trust regarding the restriction on transfer of common shares, the common shares have equal dividend, distribution, liquidation and other rights. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
Declaration of Trust provides for approval by a majority of the votes cast by holders of common shares entitled to vote on the matter in all situations permitting or requiring action
by the shareholders, except with respect to: (i)&nbsp;the election of Trustees (which requires a plurality of all the votes cast at a meeting of our shareholders at which a quorum is present);
(ii)&nbsp;the removal of Trustees (which requires the affirmative vote of the holders of two-thirds of the outstanding shares of beneficial interest entitled to vote generally in the
election of Trustees, which action can only be taken for cause by vote at a shareholder meeting); (iii)&nbsp;the merger of COPT with another entity or the sale (or other disposition) of all or
substantially all of the assets of COPT (which requires the affirmative vote of the holders of two-thirds of the outstanding shares of beneficial interest entitled to vote on the matter);
(iv)&nbsp;the amendment of the Declaration of Trust (which requires the affirmative vote of two-thirds of all the votes entitled to be cast on the matter); and (v)&nbsp;the termination
of COPT (which requires the affirmative vote of two-thirds of the outstanding shares of beneficial interest entitled to be cast on the matter). Our Declaration of Trust permits the
Trustees, without any action by the holders of common shares, (a)&nbsp;by a two-thirds vote, to amend the Declaration of Trust from time to time to qualify as a real estate investment
trust under the Code or the Maryland REIT Law and (b)&nbsp;by a majority vote to amend the Declaration of Trust to increase or decrease the aggregate number of shares of beneficial interest or the
number of shares of any class of shares of beneficial interest that we have authority to issue. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Preferred Shares  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT><FONT SIZE=2><I>The following summary of the terms and provisions of our preferred shares does not purport to be complete and
is qualified in its entirety by reference to the pertinent sections of our Declaration of Trust and the Articles Supplementary to the Declaration of Trust relating to the establishment of each series
of our preferred shares, each of which is available from us as described in the section below entitled "Where You Can Find More Information."</I></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We
issued 2,200,000 Series&nbsp;G Preferred Shares in an underwritten public offering in August 2003; 2,000,000 Series&nbsp;H Preferred Shares in an underwritten public offering in
December 2003; 3,390,000 Series&nbsp;J Preferred Shares in an underwritten public offering in July 2006; and 531,667 Series&nbsp;K Preferred Shares in a private placement in January 2007. We
contributed the proceeds of the Series&nbsp;G, Series&nbsp;H and Series&nbsp;J offerings in exchange for a number of respective Series&nbsp;G, Series&nbsp;H, and Series&nbsp;J Preferred
Units equal to the number of the applicable series of preferred shares that we sold in the respective offerings. We contributed assets acquired through the Series&nbsp;K Preferred Share issuance in
exchange for a number of respective Series&nbsp;K Preferred Units equal to the number of preferred shares that we issued to the seller in the acquisition. The terms of each series of the preferred
units are substantially equivalent to the economic terms of the respective series of preferred shares to which they relate. The terms of these outstanding series of preferred shares are as follows: </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Ranking.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares, with respect to dividend rights and rights
upon
our liquidation, dissolution or winding up, rank (i)&nbsp;prior or senior to the common shares and any other class or series of our equity securities authorized or designated in the future if the
holders of Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares shall be entitled to the receipt of dividends or of amounts distributable upon liquidation,
dissolution or winding up in preference or priority to the holders of shares of such class or series ("Junior Shares"); (ii)&nbsp;on a parity </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>8</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>with
one another and any other class or series of our equity securities authorized or designated in the future if the holders of such class or series of securities and the Series&nbsp;G,
Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares shall be entitled to the receipt of dividends and of amounts distributable upon liquidation, dissolution or winding up in
proportion to their respective amounts of accrued and unpaid dividends per share or liquidation preferences, without preference or priority of one over the other ("Parity Shares"); and
(iii)&nbsp;junior to any class or series of our equity securities authorized or designated in the future if the holders of such class or series shall be entitled to the receipt of dividends and
amounts distributable upon liquidation, dissolution or winding up in preference or priority to the holders of the Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares
("Senior Shares"). </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Dividends.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Holders of Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares Preferred Shares are entitled to
receive, when and as declared by our Board of Trustees, out of our funds legally available for payment, quarterly cash dividends on such shares at the following rates: $2.00 per year per
Series&nbsp;G Preferred Share; $1.875 per year per Series&nbsp;H Preferred Share; $1.90625 per year per Series&nbsp;J Preferred Share; and $2.80 per year per Series&nbsp;K Preferred Share.
Such dividends are cumulative from the date of original issue, whether or not in any dividend period or periods such dividends shall be declared or there shall be funds legally available for the
payment of such dividends, and are payable quarterly on January&nbsp;15, April&nbsp;15, July&nbsp;15 and October&nbsp;15 of each year (or, if not a business day, the next succeeding business
day) (each a "Dividend Payment Date"). Any dividend payable on the Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares for any partial dividend period will be
computed ratably on the basis of twelve 30-day months and a 360-day year. Dividends are payable in arrears to holders of record as they appear on our share records at the close
of business on the applicable record date, which are fixed by our Board of Trustees and which are not more than 60 nor less than 10&nbsp;days prior to such Dividend Payment Date. Holders of
Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares are not entitled to receive any dividends in excess of respective cumulative dividends on such shares. No
interest, or sum of money in lieu of interest, shall be payable in respect to any dividend payment or payments on the Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred
Shares that may be in arrears. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;When
dividends are not paid in full upon the Parity Shares, or a sum sufficient for such payment is not set apart, all dividends declared upon the Parity Shares shall be declared ratably
in proportion to the respective amounts of dividends accrued and unpaid on the Parity Shares. Except as set forth in the preceding sentence, unless dividends on the Series&nbsp;G, Series&nbsp;H,
Series&nbsp;J and Series&nbsp;K Preferred Shares equal to the full amount of accrued and unpaid dividends have been or contemporaneously are declared and paid or declared and a sum sufficient for
the payment thereof has been or contemporaneously is set apart for such payment, for all past dividend periods, no dividends shall be declared or paid or set apart for payment by us and no other
distribution of cash or other property may be declared or made, directly or indirectly, by us with respect to any Parity Shares. Unless dividends equal to the full amount of all accrued and unpaid
dividends on the Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares have been paid, or declared and set apart for payment, for all past dividend periods, no
dividends (other than dividends or distributions paid in Junior Shares or options, warrants or rights to subscribe for or purchase Junior Shares) may be declared or paid or set apart for payment by us
and no other distribution of cash or other property may be declared or made, directly or indirectly, by us with respect to any Junior Shares, nor shall any Junior Shares be redeemed, purchased or
otherwise acquired (except for a redemption, purchase or other acquisition of common shares made for purposes of our employee incentive or benefit plan or any such plan of any of our subsidiaries) for
any consideration (or any monies be paid to or made available for a sinking fund for the redemption of any such Junior Shares), directly or indirectly, by us (except by conversion into or exchange for
Junior Shares, or options, warrants or rights to subscribe for or purchase Junior Shares), nor shall any other cash or other property be paid or distributed to or for the benefit of holders of Junior
Shares. Notwithstanding the provisions described above, we shall not be prohibited from </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>9</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>(i)&nbsp;declaring
or paying or setting apart for payment any dividend or distribution on any Parity Shares or (ii)&nbsp;redeeming, purchasing or otherwise acquiring any Parity Shares, in each
case, if such declaration, payment, redemption, purchase or other acquisition is necessary to maintain our qualification as a REIT. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Liquidation Preference.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Upon any voluntary or involuntary liquidation, dissolution or winding up, before any payment or distribution by
us shall be
made to or set apart for the holders of any Junior Shares, the holders of Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares shall be entitled to receive a
liquidation preference ($25.00 per share for Series&nbsp;G, Series&nbsp;H and Series&nbsp;J and $50.00 per share for Series&nbsp;K) (the "Liquidation Preference"), plus an amount equal to all
accrued and unpaid dividends (whether or not earned or declared) to the date of final distribution to such holders; but such holders shall not be entitled to any further payment. Until the holders of
the Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares have been paid the Liquidation Preference in full, plus an amount equal to all accrued and unpaid dividends
(whether or not earned or declared) to the date of final distribution to such holders, no payment shall be made to any holder of Junior Shares upon our liquidation, dissolution or winding up. If upon
any liquidation, dissolution or winding up, our assets, or proceeds thereof, distributable among the holders of Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares
shall be insufficient to pay in full the above described preferential amount and liquidating payments on any other shares of any class or series of Parity Shares, then our assets, or the proceeds
thereof, shall be distributed among the holders of the Parity Shares ratably in the same proportion as the respective amounts that would be payable on the Parity Shares if all amounts payable thereon
were paid in full. A voluntary or involuntary liquidation, dissolution or winding up shall not include a consolidation or merger of us with or into one or more other entities, a sale or transfer of
all or substantially all of our assets or a statutory share exchange. Upon any liquidation, dissolution or winding up, after payment shall have been made in full to the holders of the Parity Shares,
any other series or class or classes of Junior Shares shall be entitled to receive any and all of our assets remaining to be paid or distributed, and the holders of the Parity Shares shall not be
entitled to share therein. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Voting Rights.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Holders of Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares will not have any voting
rights,
except as set forth below and except as otherwise required by applicable law. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
and whenever dividends on any series or class of Parity Shares shall be in arrears for six or more quarterly periods (whether or not consecutive), the number of Trustees then
constituting our Board of Trustees shall be increased by two (if not already increased by reason of similar types of provisions with respect to Parity Shares of any other class or series which is
entitled to similar voting rights (the "Voting Parity Shares")), and the holders of all Voting Parity Shares then entitled to exercise similar voting rights, voting as a single class regardless of
series, will be entitled to vote for the election of the two additional Trustees at any annual meeting of shareholders or at a special meeting of the holders of the Voting Parity Shares called for
that purpose. At any time when such right to elect Trustees
separately shall have so vested, we must call such special meeting upon the written request of the holders of record of not less than 20% of the total number of Voting Parity Shares then outstanding.
Such special meeting shall be held, in the case of such written request, within 90&nbsp;days after the delivery of such request, provided that we shall not be required to call such a special meeting
if such request is received less than 120&nbsp;days before the date fixed for the next ensuing annual meeting of shareholders and the holders of the Voting Parity Shares are offered the opportunity
to elect such Trustees at such annual meeting of shareholders. If, prior to the end of the term of any Trustee so elected, a vacancy in the office of such Trustee shall occur by reason of death,
resignation, or disability, such vacancy shall be filled for the unexpired term of such former Trustee by the appointment of a new Trustee by the remaining Trustee or Trustees so elected. Whenever
dividends in arrears on outstanding Voting Parity Shares shall have been paid and dividends thereon for the current quarterly dividend period shall have been paid or declared and set apart for
payment, then the right of the holders of the Voting Parity </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>Shares
to elect such additional two Trustees shall cease and the terms of office of such Trustees shall terminate and the number of Trustees constituting our Board of Trustees shall be reduced
accordingly. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
affirmative vote or consent of at least two-thirds of the votes entitled to be cast by the holders of the outstanding Voting Parity Shares entitled to vote on such
matters, voting as a single class, will be required to (i)&nbsp;authorize, create, increase the authorized amount of, or issue any shares of any class of Senior Shares or any security convertible
into shares of any class of Senior Shares, or (ii)&nbsp;amend, alter or repeal any provision of, or add any provision to, our Declaration of Trust or Bylaws, if such action would materially
adversely affect the voting powers, rights or preferences of the holders of the Voting Parity Shares; provided, however, that no such vote of the holders of any particular class or series of the
Voting Parity Shares shall be required if, at or prior to the time such amendment, alteration or repeal is to take effect or the issuance of any such Senior Shares or convertible security is to be
made, as the case may be, provisions are made for the redemption of all outstanding shares of the respective class or series. The amendment of or supplement to our Declaration of Trust to authorize,
create, increase or decrease the authorized amount of or to issue Junior Shares, or any shares of any class or series of Parity Shares shall not be deemed to materially adversely affect the voting
powers, rights or preferences of the holders of the Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;With
respect to the exercise of the above-described voting rights, each Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Share has one (1)&nbsp;vote per
share, except that when any other class or series of preferred shares shall have the right to vote with the Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares as a
single class, then the holders of the Series&nbsp;G, Series&nbsp;H and Series&nbsp;J Preferred Shares shall have one quarter of one (0.25) vote per $25.00 of liquidation preference and the
holders of the Series&nbsp;K Preferred Shares shall have one half of one (0.50) vote per $50.00 of liquidation preference. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Conversion.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The Series&nbsp;G, Series&nbsp;H and Series&nbsp;J Preferred Shares are not convertible into or exchangeable for any other
property
or securities. The Series&nbsp;K Preferred Shares are convertible into our common shares at any time by the holders, at the rate of 0.8163 common shares for every one Series&nbsp;K Preferred Share
("Conversion Rate"). This Conversion Rate is subject to adjustment in the event that we effect a stock split, subdivision of its then outstanding common shares, or distribution of common shares in the
form of a dividend. In addition, in the event that we effect a distribution of securities other than common shares in the form of a dividend, then the Series&nbsp;K Preferred Shares shall be
entitled to receive upon conversion, in addition to the number of common shares receivable upon such conversion, the amount of our other securities that they would have otherwise received had their
Series&nbsp;K Preferred Shares been converted into common shares. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Optional Redemption.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Shares of the Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares will not be
redeemable by
us prior to the following dates (except in certain limited circumstances relating to our maintenance of our ability to qualify as a REIT as described in the section entitled "Restrictions on Ownership
and Transfer" above and subject to the holder's right to convert such shares prior to such date in the manner as described in the section entitled "Conversion" above): August&nbsp;11, 2008 with
respect to the Series&nbsp;G Preferred Shares; December&nbsp;18, 2008 with respect to the Series&nbsp;H Preferred Shares; July&nbsp;20, 2011 with respect to the Series&nbsp;J Preferred
Shares; and January&nbsp;9, 2017 with respect to the Series&nbsp;K Preferred Shares. On or after these respective dates, we may, at our option, redeem the applicable series of preferred shares, in
whole or from time to time in part, at a cash redemption price equal to 100% of the Liquidation Preference, plus all accrued and unpaid dividends, if any, to the redemption date. The redemption price
for each series of these preferred shares (other than any portion thereof consisting of accrued and unpaid dividends) will be payable solely with the proceeds from the sale of equity securities by us
or our Operating Partnership (whether or not such sale occurs concurrently with such redemption). For purposes of the preceding sentence, "equity securities" means any common shares, preferred shares,
depositary shares, partnership or other interests, participations or other ownership interests (however designated) and any rights (other than </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>debt
securities convertible into or exchangeable at the option of the holder for equity securities (unless and to the extent such debt securities are subsequently converted into equity securities)) or
options to purchase any of the foregoing of or in us or our Operating Partnership. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
the event of a redemption of any Series&nbsp;G, Series&nbsp;H, Series&nbsp;J or Series&nbsp;K Preferred Shares, if the redemption date occurs after a dividend record date and
on or prior to the related Dividend Payment Date, the dividend payable on such Dividend Payment Date in respect of such series of shares called for redemption will be payable on such Dividend Payment
Date to the holders of record at the close of business on such dividend record date, and will not be payable as part of the redemption price for such shares. The redemption date will be selected by us
and shall not be less than 30&nbsp;days nor more than
60&nbsp;days after the date notice of redemption is sent by us. If full cumulative dividends on all outstanding Series&nbsp;G, Series&nbsp;H, Series&nbsp;J or Series&nbsp;K Preferred Shares
have not been paid or declared and set apart for payment, no Series&nbsp;G, Series&nbsp;H, Series&nbsp;J or Series&nbsp;K Preferred Shares may be redeemed unless all outstanding shares within
the applicable series of preferred shares are simultaneously redeemed and neither we nor any of our affiliates may purchase or acquire shares within the applicable series of preferred shares otherwise
than pursuant to a purchase or exchange offer made on the same terms to all holders of such series of preferred shares. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
fewer than all the outstanding shares within the Series&nbsp;G, Series&nbsp;H, Series&nbsp;J or Series&nbsp;K Preferred Shares are to be redeemed, we will select those
Series&nbsp;G, Series&nbsp;H, Series&nbsp;J or Series&nbsp;K Preferred Shares to be redeemed pro rata in proportion to the numbers of shares of the applicable series of preferred shares held
by holders (with adjustment to avoid redemption of fractional shares) or by lot or in such other manner as the Board of Trustees may determine. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Notice
of redemption will be given by publication in a newspaper of general circulation in the City of New York, such publication to be made once a week for two consecutive weeks
commencing not less than 30 nor more than 60&nbsp;days prior to the redemption date. A similar notice shall be mailed by us not less than 30&nbsp;days nor more than 60&nbsp;days prior to the
redemption date to each holder of the applicable series of preferred shares to be redeemed by first class mail, postage prepaid at such holder's address as the same appears on our share records. Any
notice which was mailed as described above will be conclusively presumed to have been duly given on the date mailed whether or not the holder receives the notice. Each notice will state:
(i)&nbsp;the redemption date, (ii)&nbsp;the number of preferred shares to be redeemed, (iii)&nbsp;the place or places where certificates for such preferred shares are to be surrendered for cash
and (iv)&nbsp;the redemption price payable on such redemption date, including, without limitation, a statement as to whether or not accrued and unpaid dividends will be (x)&nbsp;payable as part of
the redemption price or (y)&nbsp;payable on the next Dividend Payment Date to the record holder at the close of business on the relevant record date as described above. From and after the redemption
date (unless we default in the payment of our redemption obligation), dividends on the applicable series of preferred shares to be redeemed will cease to accrue, such shares will no longer be deemed
to be outstanding and all rights of the holders thereof shall cease (except (a)&nbsp;the right to receive the cash payable upon such redemption without interest thereon and (b)&nbsp;if the
redemption date occurs after a dividend record date and on or prior to the related Dividend Payment Date, the right of record holders at the close of business on such record date to receive the
dividend payable on such Dividend Payment Date). The full dividend payable on such Dividend Payment Date with respect to such the applicable series of preferred shares called for redemption will be
payable on such Dividend Payment Date to the holders of record of such shares at the close of business on the corresponding dividend record date notwithstanding the prior redemption of such shares. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares have no stated maturity and are not subject to any sinking fund or mandatory redemption
provisions except as provided under "Restrictions on Ownership and Transfer" above. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>12</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Subject
to applicable law and the limitation on purchases when dividends on the Series&nbsp;G, Series&nbsp;H and Series&nbsp;J Preferred Shares are in arrears, we may, at any time
and from time to time, purchase any Series&nbsp;G, Series&nbsp;H and Series&nbsp;J Preferred Shares in the open market, by tender or by private agreement. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Issuance of Additional Preferred Shares  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Board of Trustees has the ability to designate additional series of our preferred shares of beneficial interest by adopting an
amendment to the Declaration of Trust designating the terms of such additional series of preferred shares (a "Designating Amendment"). The preferred shares, when issued, will be fully paid and
non-assessable. Because our Board of Trustees has the power to establish the preferences, powers and rights of each series of preferred shares, subject to the rights of the holders of the
Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares, our Board may afford the holders of any series of preferred shares preferences, powers and rights, voting or
otherwise, senior to the rights of holders of common shares. The issuance of additional series of preferred shares could have the effect of delaying or preventing a change of control that might
involve a premium price for shareholders or otherwise be in their best interest. The rights, preferences, privileges and restrictions of the preferred shares of each series will be fixed by the
Designating Amendment relating to the new series. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Operating Partnership Series&nbsp;I Preferred Units  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We conduct almost all of our operations through our Operating Partnership, for which we are the managing general partner. Interests in
our Operating Partnership are in the form of common and preferred units. As of the date of this prospectus, we owned a majority of the outstanding common units and a majority of the outstanding
preferred units. The remaining preferred units in our Operating Partnership were 352,000 Series&nbsp;I Preferred Units, owned by TRC Associates Limited Partnership, Incorporated, with terms as
follows: </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Voting Rights.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Except in certain limited circumstances, at any time that COPT holds less than 90% of the outstanding partnership units
in our
Operating Partnership, any amendment to the Operating
Partnership agreement must be approved by the vote of a majority of the common and preferred units not held by us, each voting as a separate class. If we were to hold 90% or more of the outstanding
partnership units, we would have the right to amend the Operating Partnership agreement without first seeking such unitholder approval. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2><I>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Liquidation.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;In the event of the dissolution of our Operating Partnership, the holder of the Series&nbsp;I Preferred Units will be
entitled to
receive a $25.00 liquidation preference (the "Series&nbsp;I Liquidation Preference"), prior to any liquidation payment to be made to the holders of the common units but pari passu with liquidation
payments made to us as holder of the Series&nbsp;E, Series&nbsp;F, Series&nbsp;G, and Series&nbsp;H Preferred Units. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Distributions.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The holder of the Series&nbsp;I Preferred Units is entitled to receive quarterly priority percentage return payments,
prior to
distributions made to the holders of the common units but pari passu with distributions made to us as holder of the Series&nbsp;E, Series&nbsp;F, Series&nbsp;G, and Series&nbsp;H Preferred
Units, in an amount equal to a percentage of the Series&nbsp;I Liquidation Preference, which percentage equals 7.50% through September&nbsp;23, 2019, and increases thereafter. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Conversion.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The Series&nbsp;I Preferred Units are convertible into common units at a conversion rate of 0.5 common units per
Series&nbsp;I
Preferred Unit. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>13</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2><B> Depositary Shares  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We may, at our option, elect to offer fractional preferred shares, rather than full preferred shares. In the event such option is
exercised, we will issue receipts for depositary shares, each of which will represent a fraction (to be set forth in the prospectus supplement relating to the preferred shares) of a share of that
series of preferred shares. The preferred shares represented by depositary shares will be deposited under a deposit agreement between us and a bank or trust company selected by us having its principal
office in the United States and having a combined capital and surplus of at least $50,000,000. Subject to the terms of the deposit agreement, each owner of a depositary share will be entitled, in
proportion to the applicable fraction of a preferred share represented by the depositary share, to all the rights and preferences of the preferred share, represented thereby (including dividend,
voting, redemption, conversion and liquidation rights). The above description of the depositary shares is only a summary, is not complete and is subject to, and is qualified in its entirety by, the
description in the related prospectus supplement and the provisions of the deposit agreement, which will contain the form of depositary receipt. A copy of the deposit agreement will be filed with the
Securities and Exchange Commission as an exhibit to, or incorporated by reference in, the registration statement of which this prospectus is a part. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Restrictions on Ownership and Transfer  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;For us to qualify as a REIT (as defined in the Internal Revenue Code of 1986, as amended (the "Code") to include certain entities), our
shares of beneficial interest generally must be beneficially owned by 100 or more persons during at least 335&nbsp;days of a taxable year of 12&nbsp;months or during a proportionate part of a
shorter taxable year. Also, not more than 50% of the value of the outstanding shares of beneficial interest may be owned, directly or indirectly, by five or fewer individuals (under the Code) at any
time during the last half of a taxable year (other than the first year for which an election to be a REIT has been made). This test is applied by "looking through" certain shareholders which are not
individuals (e.g.,&nbsp;corporations or partnerships) to determine indirect ownership of us by individuals. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
Declaration of Trust contains certain restrictions on the number of our shares of beneficial interest that a person may own, subject to certain exceptions. Our Declaration of Trust
provides that no person may own, or be deemed to own by virtue of the attribution provisions of the Code, more than 9.8% (the "Aggregate Share Ownership Limit") of the number or value of our
outstanding shares of beneficial interest. In addition, our Declaration of Trust prohibits any person from acquiring or holding, directly or indirectly, in excess of 9.8% of our total outstanding
common shares, in value or in number of shares, whichever is more restrictive (the "Common Share Ownership Limit"). Our Board of Trustees, in its sole discretion, may exempt a proposed transferee from
the Aggregate Share Ownership Limit and the Common Share Ownership Limit (an "Excepted Holder"). However, our Board of Trustees may not grant such an exemption to any person if such exemption would
result in us being "closely held" within the meaning of Section&nbsp;856(h) of the Code or otherwise would result in our failing to qualify as a REIT. In order to be considered by our Board of
Trustees as an Excepted Holder, a person also must not own, directly or indirectly, an interest in a tenant of ours (or a tenant of any entity owned or controlled by us) that would cause us to own,
directly or indirectly, more than a 9.9% interest in such a tenant. The person seeking an exemption must represent to the satisfaction of our Board of Trustees that it will not violate the two
aforementioned restrictions. The person also must agree that any violation or attempted violation of any of the foregoing restrictions will result in the automatic transfer of the shares of stock
causing such violation to the Share Trust (as defined below). Our Board of Trustees may require a ruling from the Internal Revenue Service or an opinion of counsel, in either case in form and
substance satisfactory to our Board of Trustees, in its sole discretion, in order to determine or ensure our status as a REIT. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
Declaration of Trust further prohibits (i)&nbsp;any person from beneficially or constructively owning our shares of beneficial interest if such ownership would result in us being
"closely held" under </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>14</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>Section&nbsp;856(h)
of the Code or otherwise cause us to fail to qualify as a REIT and (ii)&nbsp;any person from transferring shares of our beneficial interest if such transfer would result in our
shares of beneficial interest being owned by fewer than 100 persons. Any person who acquires or attempts or intends to acquire beneficial or constructive ownership of our shares of beneficial interest
that will or may violate any of the foregoing restrictions on transferability and ownership, or any person who would have owned our shares of the beneficial interest that resulted in a transfer of
shares to the Share Trust, is required to give notice immediately to us and provide us with such other information as we may request in order to determine the effect of such transfer on our status as
a REIT. The foregoing restrictions on transferability and ownership will not apply if our Board of Trustees determines that it is no longer in our best interests to attempt to qualify, or to continue
to qualify, as a REIT. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
any transfer of our shares of beneficial interest occurs which, if effective, would result in any person beneficially or constructively owning shares of beneficial interest in us in
excess or in violation of the above transfer or ownership limitations (a "Prohibited Owner"), then that number of our shares of beneficial interest, the beneficial or constructive ownership of which
otherwise would cause such person to be in excess of the ownership limit (rounded to the nearest whole share), will automatically be transferred to a trust (the "Share Trust") for the exclusive
benefit of one or more charitable beneficiaries (the "Charitable Beneficiary"), and the Prohibited Owner will not acquire any rights in such shares. Such automatic transfer will be deemed to be
effective as of the close of business on the Business Day (as defined in our Declaration of Trust) prior to the date of such violative transfer. Shares of beneficial interest held in the Share Trust
will be issued and outstanding shares. The Prohibited Owner may not benefit economically from ownership of any shares of beneficial interest held in the Share Trust, may have no rights to dividends
and may not possess any other rights attributable to the shares of beneficial interest held in the Share Trust. The trustee of the Share Trust (the "Share Trustee") will have all voting rights and
rights to dividends or other distributions with respect to shares of beneficial interest held in the Share Trust, which rights will be exercised for the exclusive benefit of the Charitable
Beneficiary. Any dividend or other distribution paid prior to the discovery by us that shares of beneficial interest have been transferred to the Share Trust will be paid by the recipient of such
dividend or distribution to the Share Trustee upon demand, and any dividend or other distribution authorized but unpaid will be paid when due to the Share Trustee. Any dividend or distribution so paid
to the Share Trustee will be held in the Share Trust for the Charitable Beneficiary. The Prohibited Owner will have no voting rights with respect to shares of beneficial interest held in the Share
Trust and, subject to Maryland law, effective as of the date that such shares of beneficial interest have been transferred to the Share Trust, the Share Trustee will have the authority (at the Share
Trustee's sole discretion) to (i)&nbsp;rescind as void any vote cast by a Prohibited Owner prior to the discovery by us that such shares have been transferred to the Share Trust and
(ii)&nbsp;recast such vote in accordance with the desires of the Share Trustee acting for the benefit of the Charitable Beneficiary. However, if we have already taken irreversible trust action, then
the Share Trustee will not have the authority to rescind and recast such vote. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Within
20&nbsp;days after receiving notice from us that shares of beneficial interest have been transferred to the Share Trust, the Share Trustee will sell the shares of beneficial
interest held in the Share Trust to a person, designated by the Share Trustee, whose ownership of the shares will not violate the ownership limitations set forth in the Declaration of Trust. Upon such
sale, the interest of the Charitable Beneficiary in the shares sold will terminate and the Share Trustee will distribute the net proceeds of
the sale to the Prohibited Owner and to the Charitable Beneficiary as described below. The Prohibited Owner will receive the lesser of (i)&nbsp;the price paid by the Prohibited Owner for the shares
or, if the Prohibited Owner did not give value for the shares in connection with the event causing the shares to be held in the Share Trust (e.g.,&nbsp;a gift, devise or other such transaction), the
Market Price (as defined in the Declaration of Trust) of such shares on the day of the event causing the shares to be received by the Share Trustee and (ii)&nbsp;the price per share received by the
Share Trustee from the sale or other disposition of the common shares held in the Share Trust. Any net sale </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>15</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>proceeds
in excess of the amount payable to the Prohibited Owner will be paid immediately to the Charitable Beneficiary. If, prior to the discovery by us that shares of beneficial interest have been
transferred to the Share Trust, such shares are sold by a Prohibited Owner, then (i)&nbsp;such shares will be deemed to have been sold on behalf of the Share Trust and (ii)&nbsp;to the extent that
the Prohibited Owner received an amount for shares that exceeds the amount that such Prohibited Owner was entitled to receive as described above, such excess will be paid to the Share Trustee upon
demand. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
addition, shares of beneficial interest held in the Share Trust will be deemed to have been offered for sale to us, or our designee, at a price per share equal to the lesser of
(i)&nbsp;the price per share in the transaction that resulted in such transfer to the Share Trust (or, in the case of a devise or gift, the Market Price at the time of such devise or gift) and
(ii)&nbsp;the Market Price on the date we, or our designee, accept such offer. We will have the right to accept such offer until the Share Trustee has sold the shares of beneficial interest held in
the Share Trust. Upon such a sale to us, the interest of the Charitable Beneficiary in the shares sold will terminate and the Share Trustee will distribute the net proceeds of the sale to the
Prohibited Owner. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;All
certificates representing the common shares will bear a legend referring to the restrictions described above. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Every
owner of more than 5% (or such other percentage as required by the Code or the regulations promulgated thereunder) of all classes or series of our shares of beneficial interest,
including the common shares, is required to give written notice to us, within 30&nbsp;days after the end of each taxable year, stating the name and address of such owner, the number of shares of
each class and series of shares of beneficial interest of us which the owner beneficially owns and a description of the manner in which such shares are held. Each such owner will provide to us such
additional information as we may request in order to determine the effect, if any, of such beneficial ownership on our status as a REIT and to ensure compliance with the Aggregate Share Ownership
Limit. In addition, each shareholder will upon demand be required to provide to us such information as we may request, in good faith, in order to determine our status as a REIT and to comply with the
requirements of any taxing authority or governmental authority or to determine such compliance. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;These
ownership limitations could delay, defer or prevent a change in control of us or other transaction that might involve a premium over the then prevailing market price for the common
shares or other attributes that the shareholders may consider to be desirable. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Classification or Reclassification of Common Shares or Preferred Shares  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our Declaration of Trust authorizes the Board of Trustees to reclassify any unissued shares of common or preferred shares into other
classes or series of classes of shares and to establish the number of shares in each class or series and to set the preferences, conversion and other rights, voting powers, restrictions, limitations
and restrictions on ownership, limitations as to dividends or other distributions, qualifications and terms or conditions of redemption for each such class or series. Thus, in addition to the
Series&nbsp;G, Series&nbsp;H, Series&nbsp;J and Series&nbsp;K Preferred Shares, the Board of Trustees could authorize the issuance of other preferred shares with terms and conditions which
could also have the effect of delaying, deferring or preventing a change in control of COPT or other transaction that might involve a premium over the then prevailing market price for common shares or
other attributes that the shareholders may consider to be desirable. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Vacancies and Removal of Trustees  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Bylaws of COPT provide that any vacancy on the Board of Trustees may be filled by a majority vote of the remaining Trustees. Any
individual so elected Trustee will hold office for the unexpired term of the Trustee he or she is replacing. The Declaration of Trust provides that a Trustee may be removed at any time only for cause
upon the affirmative vote of at least two-thirds of the votes </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>16</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>entitled
to be cast in the election of Trustees, but only by a vote taken at a shareholder meeting. These provisions preclude shareholders from removing incumbent Trustees, except for cause and upon a
substantial affirmative vote, and filling the vacancies created by such removal with their own nominees. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Advance Notice of Nominations and New Business  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Bylaws provide that, with respect to an annual meeting of shareholders, nominations of persons for election to the Board of
Trustees and the proposal of business to be considered by shareholders may be made only (a)&nbsp;pursuant to COPT's notice of the meeting, (b)&nbsp;by the Board of Trustees or (c)&nbsp;by a
shareholder who is entitled to vote at the meeting and has complied with the advance notice procedures set forth in the Bylaws. With respect to special meetings of shareholders, the Bylaws provide
that only the business specified in COPT's notice of meeting may be brought before the meeting of shareholders and nominations of persons for election to the Board of Trustees may be made only
(a)&nbsp;pursuant to COPT's notice of the meeting, (b)&nbsp;by the Board of Trustees or (c)&nbsp;provided that the Board of Trustees has determined that Trustees shall be elected at such
meeting, by a shareholder who is entitled to vote at the meeting and has complied with the advance notice provisions set forth in the Bylaws. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Possible Antitakeover Effect of Certain Provisions of Maryland Law  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Maryland General Corporations Law ("MGCL") contains provisions that may be deemed to have an antitakeover effect.
The provisions applicable to COPT are set forth below. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Certain Business Combinations.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Under the MGCL, as applicable to Maryland real estate investment trusts, certain business combinations
(including
certain mergers, consolidations, share exchanges and asset transfers and certain issuances and reclassifications of equity securities) between a Maryland real estate investment trust and any person
who beneficially owns ten percent or more of the voting power of the trust's shares or an affiliate of the trust who, at any time within the two-year period prior to the date in question,
was the beneficial owner of ten percent or more of the voting power of the then outstanding voting shares of such trust (an "Interested Shareholder"), or an affiliate of such an Interested
Shareholder, are prohibited for five years after the most recent date on which the Interested Shareholder becomes an Interested Shareholder. Thereafter, any such business combination must be
recommended by the board of trustees of such trust and approved by the affirmative votes of at least (i)&nbsp;80% of the votes entitled to be cast by holders of outstanding voting shares of the
trust and (ii)&nbsp;two-thirds of the votes entitled to be cast by holders of voting shares of the trust other than shares held by the Interested Shareholder with whom (or with whose
affiliate) the business combination is to be effected, unless, among other conditions, the trust's common shareholders receive a minimum price (as defined in the MGCL) for their shares and the
consideration is received in cash or in the same form as previously paid by the Interested Shareholder for its shares. These provisions of Maryland law do not apply, however, to business combinations
that are approved or exempted by the board of trustees of the trust prior to the time that the Interested Shareholder becomes an Interested Shareholder. The Board of Trustees has opted out of this
statute by resolution. The Board of Trustees
may, however, rescind its resolution at any time to make these provisions of Maryland law applicable to COPT. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Control Share Provisions.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The MGCL generally provides that control shares of a Maryland real estate investment trust acquired in a
control share
acquisition have no voting rights unless those rights are approved by a vote of two-thirds of the disinterested shares (generally shares held by persons other than the acquiror, officers
or trustees who are employees of the trust). An acquiror is deemed to own control shares the first time that the acquiror's voting power in electing trustees equals or exceeds 20% of all such voting
power. Control shares do not include shares the acquiring person is then entitled to vote as a result of having previously obtained shareholder approval. A control share acquisition means the
acquisition of control shares, subject to certain exceptions. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>17</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;A
person who has made or proposes to make a control share acquisition, upon satisfaction of certain conditions (including an undertaking to pay expenses), may compel the Board of
Trustees to call a special meeting of shareholders to be held within 50&nbsp;days of the demand to consider whether the control shares will have voting rights. The trust may present the question at
any shareholders' meeting on its own initiative. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
voting rights are not approved at the meeting or if the acquiring person does not deliver an acquiring person statement as required by the statute, then, subject to certain conditions
and limitations, the trust may redeem any or all of the control shares (except those for which voting rights have previously been approved) for fair value, determined without regard to the absence of
voting rights for the control shares. Fair value will be determined as of the date of the last control share acquisition by the acquiror or of any meeting of shareholders at which the voting rights of
such shares are considered and not approved. If voting rights for control shares are approved at a shareholders' meeting and the acquiror becomes entitled to vote a majority of the shares entitled to
vote, all other shareholders may exercise appraisal rights. The fair value of the shares as determined for purposes of such appraisal rights may not be less than the highest price per share paid by
the acquiror in the control share acquisition. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
control share provisions do not apply (a)&nbsp;to shares acquired in a merger, consolidation or share exchange if the trust is a party to the transaction or (b)&nbsp;to
acquisitions approved or exempted by the declaration of trust or bylaws of the trust. The Bylaws contain a provision exempting from the control share acquisition statute any and all acquisitions by
any person of COPT's shares of beneficial interest. The Board of Trustees may, however, amend the Bylaws at any time to eliminate such provision, either prospectively or retroactively. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2><B> Dissolution of the Company; Termination of REIT Status  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The Declaration of Trust permits the termination of COPT and the discontinuation of the operations of COPT by the affirmative vote of
the holders of not less than two-thirds of the outstanding common shares entitled to be cast on the matter at a meeting of shareholders or by written consent. In addition, the Declaration
of Trust permits the termination of COPT's qualification as a REIT if such qualification, in the opinion of the Board of Trustees, is no longer advantageous to the shareholders. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Desp_Warr"></A>DESCRIPTION OF WARRANTS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We may issue separately, or together with any preferred shares or common shares offered by any prospectus supplement, warrants for the
purchase of other preferred shares and common shares. The warrants may be issued under warrant agreements to be entered into between us and a bank or trust company, as warrant agent, and may be
represented by certificates evidencing the warrants, all as set forth in the prospectus supplement relating to the particular series of warrants. The following summaries of certain provisions of the
warrants are not complete and are subject to, and are qualified in their entirety by reference to, all the provisions of any related warrant agreement and warrant certificate, respectively, which will
be filed with the SEC as an exhibit to, or incorporated by reference in, the registration statement of which this prospectus is a part. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;A
prospectus supplement will describe the terms of the warrants in respect of which this prospectus is being delivered including, where applicable, the
following:</FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the title of the warrants; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the aggregate number of the warrants; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the price or prices at which the warrants will be issued; </FONT></DD></DL>
</UL>
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</FONT> <FONT SIZE=2>
<A HREF="#bg11001a_main_toc">Table of Contents</A> </FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the designation, terms and number of common shares or preferred shares that may be purchased upon exercise of the
warrants; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the designation and terms of the securities, if any, with which the warrants are issued and the number of the warrants
issued with each such offered security; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the date, if any, on and after which the warrants and related preferred shares or common shares with which the warrants
are issued will be separately transferable; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the price (or manner of calculation of the price) at which each common share or preferred share may be purchased upon
exercise of the warrant; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the date on which the right to exercise the warrants will commence and the date on which the right will expire; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>the minimum or maximum amount of the warrants which may be exercised at any one time; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>information with respect to book-entry procedures, if any; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>a discussion of material federal income tax considerations; and </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>any other terms of the warrants, including terms, procedures and limitations relating to the exchange and exercise of the
warrants. </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
exercise of any warrants will be subject to, and limited by, the transfer and ownership restrictions in our Declaration of Trust. See "Description of Shares&#151;Restrictions
on Ownership and Transfer." </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Federal"></A>FEDERAL INCOME TAX MATTERS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;COPT was organized in 1988 and elected to be taxed as a REIT commencing with its taxable year ended December&nbsp;31, 1992. COPT
believes that it was organized and has operated in a manner that permits it to satisfy the requirements for taxation as a REIT under the applicable provisions of the Code and intends to continue to
operate in such a manner. No assurance can be given, however, that such requirements have been or will continue to be met. The following is a summary of the material U.S. federal income ("Federal")
tax considerations that may be relevant to COPT and its shareholders, including the continued treatment of COPT as a REIT for Federal income tax purposes. This summary is for general information
purposes only, and is not intended to be (and is
not) tax advice. For purposes of this discussion of "Federal Income Tax Matters," the term "COPT" refers only to Corporate Office Properties Trust and not to any other affiliated entities. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT><FONT
SIZE=2><B>Each prospective purchaser is advised to consult his or her tax advisor regarding the specific tax consequences to him or her of the purchase, ownership and sale
of the securities offered hereby and of our election to be taxed as a REIT, including the Federal, state, local, foreign income and other tax consequences of such purchase, ownership, sale and
election, and of potential changes in applicable tax laws.</B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
following discussion is based on the law existing and in effect on the date hereof, and COPT's qualification and taxation as a REIT will depend on compliance with such law and with
any future amendments or modifications to such law. The qualification and taxation as a REIT will further depend upon the ability to meet, on a continuing basis through actual operating results, the
various qualification tests imposed under the Code discussed below. No assurance can be given that COPT will satisfy such tests on a continuing basis. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
brief, an entity that invests primarily in real estate can, if it meets the REIT provisions of the Code described below, claim a tax deduction for the dividends it pays to its
shareholders. Such an entity generally is not taxed on its "REIT taxable income" to the extent such income is currently </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>19</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>distributed
to shareholders, thereby substantially eliminating the "double taxation" (i.e.,&nbsp;at both the entity and shareholder levels) that generally results from an investment in an entity
which is taxed as a corporation. However, as discussed in greater detail below, such an entity remains subject to tax in certain circumstances even if it qualifies as a REIT. Further, if the entity
were to fail to qualify as a REIT in any year, it would not be able to deduct any portion of the dividends it paid to its shareholders and would be subject to full Federal corporate income taxation on
its earnings, thereby significantly reducing or eliminating the cash available for distribution to its shareholders. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Morgan,
Lewis&nbsp;&amp; Bockius&nbsp;LLP has opined that, for Federal income tax purposes, COPT has properly elected and otherwise qualified to be taxed as a REIT under the Code for
taxable years commencing on or after January&nbsp;1, 1992 and that its proposed method of operations as described in this prospectus and as represented to Morgan, Lewis&nbsp;&amp; Bockius&nbsp;LLP
by COPT will enable COPT to continue to satisfy the requirements for such qualification and taxation as a REIT under the Code for future taxable years. This opinion, however, is based upon certain
factual assumptions and representations made by COPT. Moreover, such qualification and taxation as a REIT depends upon the ability of COPT to meet, for each taxable year, various tests imposed under
the Code as discussed below, and Morgan, Lewis&nbsp;&amp; Bockius&nbsp;LLP has not reviewed in the past, and may not review in the future, COPT's
compliance with these tests. Accordingly, no assurance can be given that the actual results of the operations of COPT for any particular taxable year will satisfy such requirements. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2><B> Taxation of COPT  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;General.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;In any year in which COPT qualifies as a REIT, it will not generally be subject to Federal income tax on that portion of its
REIT taxable
income or capital gain that is distributed to shareholders. COPT will, however, be subject to tax at normal corporate rates upon any taxable income or capital gains not distributed. Shareholders are
required to include their proportionate share of the REIT's undistributed long-term capital gain in income, but would receive a credit for their share of any taxes paid on such gain by the
REIT. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Notwithstanding
its qualification as a REIT, COPT also may be subject to taxation in certain other circumstances. If COPT should fail to satisfy either the 75% or the 95% gross income
test (each as discussed below), and nonetheless maintains its qualification as a REIT because certain other requirements are met, it will be subject to a 100% tax on the greater of the amount by which
COPT fails either the 75% or the 95% gross income test, multiplied by a fraction intended to reflect COPT's profitability. COPT will also be subject to a tax of 100% on net income from any "prohibited
transaction" (as described below), and if COPT has (i)&nbsp;net income from the sale or other disposition of "foreclosure property" which is held primarily for sale to customers in the ordinary
course of business or (ii)&nbsp;other non-qualifying income from foreclosure property, it will be subject to tax on such income from foreclosure property at the highest corporate rate.
In addition, if COPT should fail to distribute during each calendar year at least the sum of (i)&nbsp;85% of its REIT ordinary income for such year, (ii)&nbsp;95% of its REIT capital gain net
income for such year and (iii)&nbsp;any undistributed taxable income from prior years, COPT would be subject to a 4% excise tax on the excess of such required distribution over the amounts actually
distributed. COPT also may be subject to the corporate alternative minimum tax, as well as to tax in certain situations not presently contemplated. COPT will use the calendar year both for Federal
income tax purposes, as is required of a REIT under the Code, and for financial reporting purposes. Finally, in the event that items of rent, interest or other deductible expenses are paid to a REIT
by a "taxable REIT subsidiary" (as defined below) of such REIT, and such amounts are determined to be other than at arm's length, a REIT may be subject to a 100% tax on the portion of such amounts
treated as excessive. Safe harbors exist for certain rental payments. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2><I>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Failure to Qualify.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;If COPT fails to qualify for taxation as a REIT in any taxable year and certain relief provisions do not apply, COPT
will be
subject to tax (including any applicable alternative minimum tax) on its taxable income at regular corporate rates. Distributions to shareholders in any </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>20</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>year
in which COPT fails to qualify as a REIT will not be deductible by COPT, nor generally will they be required to be made under the Code. In such event, to the extent of current and accumulated
earnings and profits, all distributions to shareholders will be taxable as dividend income, and subject to certain limitations in the Code, corporate distributees may be eligible for the dividends
received deduction. Unless entitled to relief under specific statutory provisions, COPT also will be disqualified from reelecting taxation as a REIT for the four taxable years following the year
during which qualification was lost. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> REIT Qualification Requirements  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In order to qualify as a REIT, COPT must meet the following requirements, among others: </FONT></P>


<P style="font-family:times;"><FONT SIZE=2><I>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Share Ownership Tests.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;COPT's shares of beneficial interest must be held by a minimum of 100 persons for at least 335&nbsp;days in each
taxable
year (or a proportionate number of days in any short taxable year). In addition, at all times during the second half of each taxable year, no more than 50% in value of the outstanding shares of
beneficial interest of COPT may be owned, directly or indirectly and taking into account the effects of certain constructive ownership rules, by five or fewer individuals, which for this purpose
includes certain tax-exempt entities (the "50% Limitation"). However, for purposes of this test, any shares of beneficial interest held by a qualified domestic pension or other retirement
trust will be treated as held directly by its beneficiaries in proportion to their actuarial interest in such trust rather than by such trust. In addition, for purposes of the 50% Limitation, shares
of beneficial interest owned, directly or indirectly, by a corporation will be considered as being owned proportionately by its shareholders. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
order to attempt to ensure compliance with the foregoing share ownership tests, COPT's Declaration of Trust places certain restrictions on the transfer of its shares of beneficial
interest to prevent additional concentration of share ownership. Moreover, to evidence compliance with these requirements, Treasury Regulations require COPT to maintain records which disclose the
actual ownership of its outstanding shares of beneficial interest. In fulfilling its obligations to maintain records, COPT must and will demand written statements each year from the record holders of
designated percentages of its shares of beneficial interest disclosing the actual owners of such shares of beneficial interest (as prescribed by Treasury Regulations). A list of those persons failing
or refusing to comply with such demand must be maintained as part of COPT's records. A shareholder failing or
refusing to comply with COPT's written demand must submit with his tax return a similar statement disclosing the actual ownership of COPT shares of beneficial interest and certain other information. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Asset Tests.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;At the close of each quarter of COPT's taxable year, COPT must satisfy two tests relating to the nature of its assets
(determined in
accordance with generally accepted accounting principles). First, at least 75% of the value of COPT's total assets must be represented by interests in real property, interests in mortgages on real
property, shares in other REITs, cash (including in some instances, with respect to our taxable years beginning January&nbsp;1, 2009, foreign currency), cash items, government securities and
qualified temporary investments. Second, although the remaining 25% of COPT's assets generally may be invested without restriction, securities in this class may not exceed (i)&nbsp;in the case of
securities of any one non-government issuer, 5% of the value of COPT's total assets (the "REIT Value Test") or (ii)&nbsp;10% of the outstanding voting securities or outstanding value of
any one such issuer (collectively, the "Issuer Tests"). </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
REIT Value Test and the Issuer Tests will not, however, apply to securities held by a REIT in a "taxable REIT subsidiary," so long as, at of the close of each quarter of each taxable
year, not more than 25% (20% with respect to our taxable years ended on or before December&nbsp;31, 2008) of COPT's total assets are represented by securities of taxable REIT subsidiaries. A
corporation will qualify as a taxable REIT subsidiary with respect to COPT only if (i)&nbsp;either (x)&nbsp;COPT directly or indirectly owns stock in such corporation and COPT and such corporation
jointly make a taxable REIT subsidiary </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>election
in accordance with applicable procedures or (y)&nbsp;a taxable REIT subsidiary of COPT owns, directly or indirectly, securities possessing more than 35% of the total voting power of the
outstanding securities of such corporation or securities having a value of more than 35% of the total value of the outstanding securities of such corporation and (ii)&nbsp;such corporation does not
directly or indirectly (x)&nbsp;operate or manage a lodging or health care facility or (y)&nbsp;provide to any other person (under a franchise, license or otherwise) rights to any brand name under
which any lodging facility or health care facility is operated. Here, however, it should be noted that in certain limited circumstances a taxable REIT subsidiary may be permitted to provide rights to
an "eligible independent contractor" to operate or manage a lodging facility (or, with respect to our taxable years beginning after January&nbsp;1, 2009, a health care facility) without running
afoul of these rules. For purposes of this paragraph, references to a "lodging facility" are to a hotel, motel or other establishment more than one-half of the dwelling units in which are
used on a transient basis and references to a "health care facility" are to a hospital, nursing facility, assisted living facility, congregate care facility, qualified continuing care facility or
other licensed facility which extends medical, nursing or ancillary services to patients. Taxable REIT subsidiaries are subject to full corporate level taxation on their earnings, but are permitted to
engage in certain types of real estate management activities and certain other activities which cannot currently be performed by REITs or their controlled subsidiaries without jeopardizing REIT
status. On January&nbsp;1, 2001, our operating partnership acquired all of the stock in Corporate Office Management,&nbsp;Inc. ("COMI") that was not previously owned by it, and we elected to
treat COMI as a taxable REIT subsidiary effective January&nbsp;1, 2001. Thus, COMI is and will remain fully taxable with respect to its earnings. The election will, however, generally allow COMI to
continue its real estate management activities without jeopardizing our REIT status. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
addition, certain debt securities held by a REIT will not be taken into account for purposes of the Issuer Value Test. Where COPT invests in a partnership (such as the Operating
Partnership), it will be deemed to own a proportionate share of the partnership's assets, and the partnership interest will not constitute a security for purposes of these tests. Accordingly, COPT's
investment in real properties through its interests in the Operating Partnership (which itself holds real properties through other partnerships) will constitute an investment in qualified assets for
purposes of the 75% asset test. However, solely for purposes of the 10% value test, described above, the determination of a REIT's interest in partnership assets will be based on the REIT's
proportionate interest in any securities issued by the partnership, excluding for these purposes, certain excluded securities as described in the Code. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
we failed to meet the Issuer Tests at the end of any quarter and did not cure such failure within 30&nbsp;days thereafter, we still could avoid disqualification by disposing of
sufficient assets or otherwise complying with such asset test within six months of the identification of the failure, provided the failure was due to assets the value of which did not exceed the
lesser of 1% of the value of our assets at the end of the relevant quarter and $10,000,000. For violations of any of the REIT asset tests due to reasonable cause that were larger than this amount, we
still could avoid disqualification by taking certain steps including (x)&nbsp;disposing of sufficient assets to meet the asset tests or otherwise complying with such asset tests,
(y)&nbsp;preparing a schedule for the quarter describing the non- qualifying assets and filing it in accordance with regulations and (z)&nbsp;paying a tax equal to the greater of
$50,000 or 35% of the net income generated by the non-qualifying assets. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Gross Income Tests.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;There are two separate percentage tests relating to the sources of COPT's gross income which must be satisfied for
each taxable
year. For purposes of these tests, where COPT invests in a partnership, COPT will be treated as receiving its share of the income and loss of the partnership based on its capital interest in such
partnership, and the gross income of the partnership will retain the same character in the hands of COPT as it has in the hands of the partnership. The two tests are described below. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The 75% Test.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;At least 75% of COPT's gross income for the taxable year must be "qualifying income." Qualifying income generally
includes:
(i)&nbsp;rents from real property (except as modified below); </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>(ii)&nbsp;interest
on obligations secured by mortgages on, or interests in, real property; (iii)&nbsp;gains from the sale or other disposition of interests in real property and real estate
mortgages, other than gain from property held primarily for sale to customers in the ordinary course of COPT's trade or business ("dealer property"); (iv)&nbsp;dividends or other distributions on
shares in other REITS, as well as gain from the sale of such shares; (v)&nbsp;abatements and refunds of real property taxes; (vi)&nbsp;income from the operation, and gain from the sale, of
property acquired at or in lieu of a foreclosure of the mortgage secured by such property ("foreclosure property"); and (vii)&nbsp;commitment fees received for agreeing to make loans secured by
mortgages on real property or to purchase or lease real property. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Rents
received or accrued from a tenant will not qualify as "rents from real property" for purposes of the 75% gross income test or the 95% gross income test, described below, if COPT,
or a person owning, actually or under applicable constructive ownership rules, a 10% or greater interest in COPT, directly or constructively owns 10% or more of such tenant, unless (i)&nbsp;such
rents are received or accrued from a taxable REIT subsidiary and (ii)&nbsp;either (x)&nbsp;at least 90% of the leased property in respect of which COPT is receiving or accruing such rents is
occupied by persons other than taxable REIT subsidiaries of COPT and the amounts paid to COPT by the taxable REIT subsidiary as rents with respect to such property are substantially comparable to
rents paid by other tenants of such property or (y)&nbsp;such rents are received in respect of a "qualified lodging facility" (or, with respect to our taxable years beginning after January&nbsp;1,
2009, a "qualified healthcare facility") where such facility is operated on behalf of the taxable REIT subsidiary by a person who is an "eligible independent contractor" (as such term is defined for
purposes of the REIT provisions of the Code). In addition, if rent attributable to personal property leased in connection with a lease of real property is greater than 15% of the total rent received
under the lease, then the portion of rent attributable to such personal property will not qualify as rents from real property. Moreover, an amount received or accrued will not qualify as rents from
real property (or as interest income) for purposes of the 75% and 95% gross income tests if it is based in whole or in part on the income or profits of any person, although an amount received or
accrued generally will not be excluded from "rents from real property" solely by reason of being based on a fixed percentage or percentages of receipts or sales. Finally, for rents received to qualify
as rents from real property for purposes of the 75% and 95% gross income tests, COPT generally must not operate or manage the property or furnish or render services to customers, other than through an
"independent contractor" from whom COPT derives no income, or through a taxable REIT subsidiary, except that the "independent contractor" or taxable REIT subsidiary requirement does not apply to the
extent that the services provided by COPT are "usually or customarily rendered" in connection with the rental of space for occupancy only, and are not otherwise considered "rendered to the occupant
for his convenience." In addition, COPT may directly perform a </FONT><FONT SIZE=2><I>de minimis</I></FONT><FONT SIZE=2> amount of non-customary services. COPT believes that the services
provided with regard to COPT's properties by the Operating Partnership (or its agents) have been (and, it is believed, will in the future be) usual or customary services. Any services that cannot be
provided directly by the Operating Partnership will be performed by independent contractors or a taxable REIT subsidiary. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The 95% Test.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;In addition to deriving 75% of its gross income from the sources listed above, at least 95% of COPT's gross income for
the taxable year
must be derived from the above-described qualifying income or from dividends, interest, or gains from the sale or other disposition of stock or other
securities that are not dealer property. Dividends and interest on obligations not collateralized by an interest in real property are included for purposes of the 95% test, but not for purposes of the
75% test. COPT intends to monitor closely its non-qualifying income and anticipates that non-qualifying income from its activities will not result in COPT failing to satisfy
either the 75% or 95% gross income test. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Except
to the extent provided by Treasury regulations, any income from a hedging transaction we enter into in the normal course of our business primarily to manage risk of interest rate
or price changes or currency fluctuations with respect to borrowings made or to be made, or ordinary </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>23</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>obligations
incurred or to be incurred, to acquire or carry real estate assets, which is clearly identified as specified in Treasury regulations before the close of the day on which it was acquired,
originated, or entered into, including gain from the sale or disposition of such a transaction, will not constitute gross income for purposes of the 95% gross income test (and will constitute
non-qualifying income for purposes of the 75% gross income test). Income and gain from such hedging transactions entered into after July&nbsp;30, 2008 (and hedging transactions entered
into primarily to manage the risk of currency fluctuations with respect to any item of income or gain that would be qualifying income under the 75% or 95% gross income tests) will be excluded from
gross income for purposes of both the 75% and 95% tests. Similarly, certain foreign currency gains recognized after July&nbsp;30, 2008 will be excluded from gross income for purposes of these tests. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;For
purposes of determining whether COPT complies with the 75% and the 95% gross income tests, gross income does not include income from prohibited transactions. A "prohibited
transaction" is a sale of dealer property (excluding foreclosure property); however, a sale of property will not be a prohibited transaction if such property is held for at least two years (or, for
sales made before July&nbsp;31, 2008, four years) and certain other requirements&#151;such as those relating to the number of properties sold in a year, their tax bases and the cost of
improvements made thereto&#151;are satisfied. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Even
if COPT fails to satisfy one or both of the 75% and 95% gross income tests for any taxable year, it may still qualify as a REIT for such year if it is entitled to relief under
certain provisions of the Code. These relief provisions will generally be available if: (i)&nbsp;COPT's failure to comply is due to reasonable cause and not to willful neglect; (ii)&nbsp;COPT
reports the nature and amount of each item of its income included in the tests on a schedule attached to its tax return; and (iii)&nbsp;any incorrect information on this schedule is not due to fraud
with intent to evade tax. If these relief provisions apply, however, COPT will nonetheless be subject to a tax equal to (i)&nbsp;the greater of the amount by which it fails either the 75% or 95%
gross income test, multiplied by (ii)&nbsp;a fraction intended to reflect COPT's profitability. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Compliance with Income Tests.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;COPT intends to continue to monitor its operations and investments so as to continue to satisfy the 75%
and 95% gross
income tests. While the Operating Partnership or its affiliates provide certain services with respect to the properties in which COPT owns interests and possibly with respect to any newly acquired
properties, COPT believes that for purposes of the 75% and 95% gross income tests the services provided at such properties and any other services and amenities provided by the Operating Partnership or
its agents with respect to such properties will be of the type usually or customarily rendered in connection with the rental of space for occupancy only and not rendered to the occupants of such
properties. COPT intends that services that cannot be provided directly by the Operating Partnership or other agents will be performed by independent contractors or taxable REIT subsidiaries. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Annual Distribution Requirements.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;In order to qualify as a REIT, COPT is required to distribute dividends to its shareholders each year
in an amount
at least equal to (i)&nbsp;the sum of (A)&nbsp;90% of COPT's REIT taxable income (computed without regard to the dividends paid deduction and COPT's net capital gain) and (B)&nbsp;90% of the net
income (after tax), if any, for foreclosure property, minus (ii)&nbsp;the sum of certain items of non-cash income. Such distributions must be paid in the taxable year to which they
relate, or in the following taxable year if declared before COPT timely files its tax return for the prior year and if paid on or before the first regular dividend payment after the declaration. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;COPT
intends to make timely distributions sufficient to satisfy the annual distribution requirements. In this regard, the Operating Partnership agreement authorizes COPT in its capacity
as General Partner to take such steps as may be necessary to cause the Operating Partnership to distribute to its partners an amount sufficient to permit COPT to meet the distribution requirements. It
is possible that COPT may not have sufficient cash or other liquid assets to meet the above-described distribution requirement, either due to timing differences between the actual receipt of income
and </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>24</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>actual
payment of expenses on the one hand, and the inclusion of such income and deduction of such expenses in computing COPT's REIT taxable income on the other hand, or for other reasons. COPT will
monitor closely the relationship between its REIT taxable income and cash flow and, if necessary, arrange for borrowings to raise cash or take such other steps as it deems necessary in order to
satisfy the distribution requirement. In addition, from time to time, COPT may declare taxable dividends payable in cash or stock at the election of the COPT shareholders, subject to a limit on the
aggregate amount of cash that could be paid. IRS guidance permits COPT to make distributions of its shares (in lieu of cash) on or before December&nbsp;31, 2012 in respect of taxable years ending on
or before December&nbsp;31, 2011, that will be considered taxable distributions in an amount equal to the amount of cash that could have been received instead of such shares. This temporary
flexibility with respect to distributions is available provided certain requirements are satisfied, including that 10% or more of the
distribution is payable in cash. However, there can be no assurance that a borrowing or share distribution will be available or practicable at any particular time. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
COPT fails to meet the above-described distribution requirement as a result of an adjustment to COPT's tax return by the Service, COPT may retroactively cure the failure by paying a
"deficiency dividend" (plus applicable penalties and interest) within a specified period. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
we fail to satisfy one or more requirements for REIT qualification (other than the 75% and 95% gross income tests and other than the requirements necessary to cure a failure of the
asset tests, as described above), we can avoid disqualification if our failure is due to reasonable cause and not willful neglect, and we pay a penalty of at least $50,000 (and, in some cases, more)
for each such failure. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B> Taxation of Shareholders  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Taxation of Taxable Domestic Shareholders.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;As long as COPT qualifies as a REIT, distributions made to its taxable domestic shareholders
out of
current or accumulated earnings and profits (and not designated as capital gain dividends) will constitute dividends taxable as ordinary income, and domestic corporate shareholders will not be
eligible for the dividends received deduction as to such amounts. In determining the extent to which a distribution with respect to the common shares constitutes a dividend for tax purposes, our
earnings and profits will be allocated, on a pro rata basis, first to distributions with respect to any class of preferred shares, and then to our common shares. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"Qualified
dividend income" received by non-corporate U.S. shareholders will generally be subject to Federal income tax at the rate applicable to long-term
capital gains (currently at a maximum rate of 15% through 2012). Qualified dividend income generally includes dividends paid by domestic "C" corporations and certain qualified foreign corporations to
most non-corporate U.S. shareholders. In general, dividends payable by REITs are not eligible for the reduced tax rate on corporate dividends, except to the extent that certain holding
period requirements are met and the REIT's dividends are attributable to dividends received from taxable corporations (such as taxable REIT subsidiaries) or to income that was subject to Federal
income tax at the corporate/REIT level (for example, if the REIT distributes taxable income that it had retained and paid tax on in the preceding taxable year). The currently applicable provisions of
the Federal income tax laws relating to qualified dividend income are currently scheduled to "sunset," or revert back to prior provisions of law, effective for taxable years beginning after
December&nbsp;31, 2012, at which time the capital gains rate is scheduled to be increased to 20% and the rate applicable to dividends is scheduled to be increased to the tax rate then applicable to
ordinary income. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Distributions
in excess of current and accumulated earnings and profits will not be taxable to a shareholder to the extent that they do not exceed the adjusted basis of the shareholder's
shares of beneficial interest, but rather will reduce the adjusted basis of such shares. To the extent that such distributions exceed the adjusted basis of a shareholder's shares of beneficial
interest, they will be </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>included
in income as short-term or long-term capital gain (depending on the length of time the shares have been held), assuming the shares are capital assets in the hands of
the shareholder. In addition, any dividend declared by COPT in October, November or December of any year and payable to a shareholder of record on a specific date in any such month shall be treated as
both paid by COPT and received by the shareholder on December&nbsp;31 of such year, provided that the dividend is actually paid by COPT during January of the following calendar year. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Domestic
shareholders may not include in their individual income tax returns any of COPT's net operating losses or capital losses. Instead, such losses would be carried over by COPT for
potential offset against future income (subject to certain limitations). Distributions made by COPT and gain arising from the sale or exchange of shares will not be treated as passive activity income,
and, as a result, shareholders generally will not be able to apply any "passive losses" against such income and gain. In addition, taxable distributions from COPT generally will be treated as
investment income. Capital gain dividends (including distributions treated as such) and capital gain from the disposition of shares, however, will be treated as investment income only if a shareholder
so elects, in which case such capital gain will be taxed at ordinary income rates. COPT will notify shareholders after the close of its taxable year as to the portions of distributions attributable to
that year that constitute ordinary income, return of capital and capital gain. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
general, a domestic shareholder will realize capital gain or loss on the disposition of COPT's shares of beneficial interest equal to the difference between (i)&nbsp;the amount of
cash and the fair market value of any property received on such disposition, and (ii)&nbsp;the shareholder's adjusted basis of such shares of beneficial interest. Such gain or loss generally will
constitute short-term capital gain or loss if the shareholder has not held such shares for more than one year and long-term capital gain or loss if the shareholder has held
such shares for more than one year. See the section below entitled "Capital Gains and Losses." Loss upon a sale or exchange of COPT's shares of beneficial interest by a shareholder who has held such
shares for six months or less (after applying certain holding period rules) will be treated as a long-term capital loss to the extent of distributions from COPT required to be treated by
such shareholder as long-term capital gain. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Capital Gains and Losses.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The current maximum marginal individual income tax rate is 35%. The
current maximum tax rate on net capital gains applicable to individuals, trusts and estates from the sale or exchange of capital assets held for more than one year is 15% (through 2012). For
individuals, trusts and estates who would be subject to a maximum tax rate of 10%, the current rate on net capital gains is reduced to 5%. Accordingly, the tax rate differential between capital gain
and ordinary income for noncorporate taxpayers may be significant. In addition, the characterization of income as capital or ordinary may affect the deductibility of capital losses. Capital losses not
offset by capital gains may be deducted against a noncorporate taxpayer's ordinary income only up to a maximum annual amount of $3,000. Unused capital losses may be carried forward. All net capital
gain of a corporate taxpayer is subject to tax at ordinary corporate rates. A corporate taxpayer can deduct capital losses only to the extent of capital gains, with unused losses being carried back
three years and forward five years. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
a shareholder recognizes a loss upon a subsequent disposition of our common shares in an amount that exceeds a prescribed threshold, it is possible that the provisions of Treasury
Regulations involving "reportable transactions" could apply, with a resulting requirement to separately disclose the loss generating transaction to the IRS. In addition, significant penalties are
imposed for failure to comply with these requirements. You should consult your own tax advisors concerning any possible disclosure obligation with respect to the ownership or disposition of our common
shares, or transactions that might be undertaken directly or indirectly by us. Moreover, you should be aware that we and other participants in transactions involving us (including advisors) might be
subject to disclosure or other requirements pursuant to these regulations. </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Backup Withholding.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;COPT will report to its domestic shareholders and the IRS the amount of dividends paid during each calendar year
and the amount
of tax withheld, if any, with respect thereto. Under the backup withholding rules, a shareholder may be subject to backup withholding (at a current rate of 28%, but scheduled to increase to 31% for
taxable years beginning after December&nbsp;31, 2012) with respect to dividends paid unless such holder (i)&nbsp;is a corporation or comes within certain other exempt categories and, when
required, demonstrates this fact or (ii)&nbsp;provides a taxpayer identification number, certifies as to no loss of exemption and otherwise complies with the applicable requirements of the backup
withholdings rules. Any amount paid as backup withholding will be creditable against the shareholder's income tax liability. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
addition, COPT may be required to withhold a portion of capital gain distributions made to shareholders that fail to certify their non-foreign status to COPT. See section
below entitled "Taxation of Foreign Shareholders." </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Taxation of Tax-Exempt Shareholders.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The IRS has ruled that amounts distributed as dividends by a REIT generally do not constitute
unrelated business taxable income ("UBTI") when received by a tax-exempt entity. Based on that ruling, dividend income from COPT's shares of beneficial interest should not be UBTI to a
tax-exempt shareholder, provided that the tax-exempt shareholder has not held its shares as "debt financed property" within the meaning of the Code and such shares are not
otherwise used in a trade or business. Similarly, income from the sale of COPT's shares of beneficial interest will not constitute UBTI unless such tax-exempt shareholder has held such
shares as "debt financed property" within the meaning of the Code or has used the shares in a trade or business. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Notwithstanding
the above, however, a portion of the dividends paid by a "pension held REIT" will be treated as UBTI as to any trust which is described in Section&nbsp;401(a) of the
Code, is tax-exempt under Section&nbsp;501(a) of the Code (a "qualified trust") and which holds more than 10% (by value) of the interests in the REIT. A REIT is a "pension held REIT" if
(i)&nbsp;it would not have qualified as a REIT but for the application of a "look-through" exception to the 50% Limitation applicable to qualified trusts, and (ii)&nbsp;either
(A)&nbsp;at least one such qualified trust holds more than 25% (by value) of the interests in the REIT, or (B)&nbsp;one or more such qualified trusts, each of which owns more than 10% (by value)
of the interests in the REIT, hold in the aggregate more than 50% (by value) of the interests in the REIT. The percentage of any REIT dividend treated as UBTI is equal to the ratio of (i)&nbsp;the
gross income (less direct expenses related thereto) of the REIT from unrelated trades or businesses (determined as if the REIT were a qualified trust) to (ii)&nbsp;the total gross income (less
direct expenses related thereto) of the REIT. A </FONT><FONT SIZE=2><I>de minimis</I></FONT><FONT SIZE=2> exception applies where this percentage is less than 5% for any year. The provisions
requiring qualified trusts to treat a portion of REIT distributions as UBTI will not apply if the REIT is able to satisfy the 50% Limitation without relying upon the "look-through"
exception with respect to qualified trusts. As a result of certain limitations on transfer and ownership of COPT's shares of beneficial interest contained in the Charter, COPT does not expect to be
classified as a "pension held REIT." </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;New Medicare Tax on Net Investment Income.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The recently enacted Patient Protection and Affordable Care Act of 2010, as amended by the
Health Care and
Education Reconciliation Act of 2010, is scheduled to impose a 3.8% Medicare tax on certain net investment income earned by individuals, estates and trusts for taxable years beginning after
December&nbsp;31, 2012. For these purposes, net investment income generally includes a shareholder's allocable share of our income and gain realized by a shareholder from a sale of our common
shares. In the case of an individual, the tax will be imposed on the lesser of (i)&nbsp;the shareholder's net investment income or (ii)&nbsp;the amount by which the shareholder's modified adjusted
gross income exceeds $250,000 (if the shareholder is married and filing jointly or a surviving spouse), $125,000 (if the shareholder is married and filing separately) or $200,000 (in any other case).
In the case of an estate or trust, the tax will be imposed on the lesser of (i)&nbsp;undistributed net investment income or (ii)&nbsp;the excess adjusted gross income over the dollar amount at
which the highest income tax bracket applicable to an estate or trust begins. </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2><I>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Taxation of Foreign Shareholders.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The rules governing the Federal income taxation of the ownership and disposition of COPT's shares of
beneficial
interest by persons that are, for purposes of such taxation, nonresident alien individuals, foreign corporations, foreign partnerships and other foreign shareholders (collectively,
"Non-U.S. Shareholders") are complex and no attempt will be made herein to provide more than a summary of such rules. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;PROSPECTIVE
NON-U.S. SHAREHOLDERS SHOULD CONSULT WITH THEIR TAX ADVISORS TO DETERMINE THE IMPACT OF FEDERAL, STATE, AND LOCAL INCOME TAX LAWS WITH REGARD TO AN INVESTMENT IN
COPT'S SHARES OF BENEFICIAL INTEREST, INCLUDING ANY REPORTING REQUIREMENTS, AS WELL AS THE TAX TREATMENT OF SUCH AN INVESTMENT UNDER THEIR HOME COUNTRY LAWS. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
general, Non-U.S. Shareholders will be subject to regular Federal income taxation with respect to their investment in COPT's shares of beneficial interest in the same
manner as a U.S. shareholder (i.e.,&nbsp;at graduated rates on a net basis, after allowance of deductions) if such investment is "effectively connected" with the conduct by such Non-U.S.
Shareholder of a trade or business in the United States. A Non-U.S. Shareholder that is a corporation and that receives income with respect to its investment in COPT's shares of beneficial
interest that is (or is treated as) "effectively connected" with the conduct of a trade or business in the United States may
also be subject to the 30% branch profits tax imposed under Section&nbsp;884 of the Code, which is payable in addition to the regular Federal corporate income tax. The following discussion addresses
only the federal income taxation of Non-U.S. Shareholders whose investment in COPT's shares of beneficial interest is not "effectively connected" with the conduct of a trade or business in
the United States. Prospective investors whose investment in COPT's shares of beneficial interest may be "effectively connected" with the conduct of a United States trade or business should consult
their own tax advisors as to the tax consequences thereof. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Distributions
that are not attributable to gain from sales or exchanges of United States real property interests and that are not designated by COPT as capital gains dividends will be
treated as dividends of ordinary income to the extent that they are made out of COPT's current or accumulated earnings and profits. Such distributions ordinarily will be subject to a withholding tax
equal to 30% of the gross amount of the distribution unless an applicable tax treaty reduces or eliminates that tax. Dividends paid to an address in a country outside the United States will not be
presumed to be paid to a resident of such country for purposes of determining the applicability of withholding discussed above and the availability of a reduced tax treaty rate. A Non-U.S.
Shareholder who wishes to claim the benefit of an applicable treaty rate will now be required to satisfy certain certification and other requirements. Distributions that COPT makes in excess of its
current and accumulated earnings and profits will not be taxable to a Non-U.S. Shareholder to the extent they do not exceed the adjusted basis of such Non-U.S. Shareholder's
shares, but rather will reduce the adjusted basis of such shares (but not below zero). To the extent that such distributions exceed the adjusted basis of a Non-U.S. Shareholder's shares,
they will give rise to tax liability if such Non-U.S. Shareholder would otherwise be subject to tax on any gain from the sale or disposition of shares, as described below. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;For
withholding tax purposes, COPT is currently required to treat all distributions as if made out of its current or accumulated earnings and profits and thus intends to withhold at the
rate of 30% (or a reduced treaty rate if applicable) on the amount of any distribution (other than distributions designated as capital gain dividends) made to a Non-U.S. Shareholder. COPT
would not be required to withhold at the 30% rate on distributions COPT reasonably estimates to be in excess of its current and accumulated earnings and profits. If it cannot be determined at the time
a distribution is made whether such distribution will be in excess of current and accumulated earnings and profits, the distribution will be subject to withholding at the rate applicable to ordinary
dividends. However, a Non-U.S. Shareholder may seek a refund of such amounts from the IRS if it is subsequently determined that such distribution was, in fact, in excess of its current or
accumulated earnings and profits, and the </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>amount
withheld exceeded the Non-U.S. Shareholder's Federal tax liability, if any, with respect to the distribution. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;For
any year in which COPT qualifies as a REIT, distributions that are attributable to gain from sales or exchanges of United States real property interests will be taxed to a
Non-U.S. Shareholder under the provisions of the Foreign Investment in Real Property Tax Act of 1980 ("FIRPTA"). Under FIRPTA, these distributions are taxed to a Non-U.S.
Shareholder as if such gain were effectively connected with the conduct of a United States trade or business. Non-U.S. Shareholders would thus be taxed at the normal capital gain rates
applicable to domestic shareholders (subject to applicable alternative minimum tax and special alternative minimum tax in the case of nonresident alien individuals), without regard as to whether such
distributions are designated by COPT as capital gain dividends. Also, distributions subject to FIRPTA may be subject to a 30% branch profits tax in the hands of a foreign corporate shareholder not
entitled to treaty exemption. COPT is required by Treasury Regulations to withhold 35% of any distribution to a Non-U.S. Shareholder that could be designated as a capital gain dividend.
This amount is creditable against the Non-U.S. Shareholder's FIRPTA tax liability. However, the 35% withholding tax will not apply to any capital gain dividend with respect to any class of
our stock which is regularly traded on an established securities market located in the United States if the non-U.S. Shareholder did not own more than 5% of such class of stock at any time
during the taxable year. Instead any capital gain dividend will be treated as dividends of ordinary income to the extent that they are made out of our current or accumulated earnings and profits,
subject to a withholding tax equal to 30% of the gross amount of the distribution unless an applicable tax treaty reduces or eliminates that tax. Also, the branch profits tax will not apply to such a
distribution. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Gain
recognized by a Non-U.S. Shareholder upon a sale of COPT's shares of beneficial interest generally will not be subject to United States taxation unless such shares
constitute a "United States real property interest" within the meaning of FIRPTA. COPT's shares of beneficial interest will not constitute a "United States real property interest" so long as COPT is a
"domestically controlled REIT." A "domestically controlled REIT" is generally a REIT in which at all times during a specified testing period less than 50% in value of its share was held directly or
indirectly by Non-U.S. Shareholders. COPT believes that it will be a "domestically controlled REIT" and therefore, the sale of COPT's shares of beneficial interest will not be subject to
taxation under FIRPTA. However, because COPT's shares of beneficial interest are publicly traded, no assurance can be given that COPT will continue to be a "domestically controlled REIT."
Notwithstanding the foregoing, gain from the sale or exchange of its shares not otherwise subject to FIRPTA generally will be taxable to a Non-U.S. Shareholder if the Non-U.S.
Shareholder is a nonresident alien individual who is present in the United States for 183&nbsp;days or more during the taxable year and has a "tax home" in the United States. In such case, the
nonresident alien individual will be subject to a 30% United States withholding tax on the amount of such individual's gain. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
COPT does not qualify as or ceases to be a "domestically controlled REIT," whether gain arising from the sale or exchange by a Non-U.S. Shareholder of COPT's shares of
beneficial interest would be subject to U.S. taxation under FIRPTA will depend on whether the shares are "regularly traded" (as defined in applicable Treasury Regulations) on an established securities
market (such as the NYSE, on which COPT's common shares and Series&nbsp;F, G and H Preferred Shares of beneficial interest are traded) and on the size of the selling Non-U.S.
Shareholder's interest in COPT. If the gain on the sale of COPT's shares of beneficial interest were to be subject to tax under FIRPTA, the Non-U.S. Shareholder would be subject to the
same treatment as a domestic shareholder with respect to such gain (subject to applicable alternative minimum tax and a special alternative minimum tax in the case of nonresident alien individuals,
and the purchaser would be required to withhold and remit to the IRS 10% of the sale price. In addition, if COPT is not a "domestically controlled REIT," distributions in </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>excess
of its current and accumulated earnings and profits would be subject to withholding at a rate of 10%. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Dividends
paid in the United States with respect to COPT's shares of beneficial interest, and proceeds from the sale of COPT's shares of beneficial interest, through a United States
broker (or certain brokers having significant connections with the United States) may be subject to the information reporting requirements of the Code. Under the backup withholding rules, a
shareholder may be subject to backup withholding (at a current rate of 28%, but scheduled to increase to 31% for taxable years beginning after December&nbsp;31, 2012) unless such shareholder
(i)&nbsp;is a corporation or comes within certain other exempt categories and, when required, demonstrates this fact, or (ii)&nbsp;provides a taxpayer identification number and certifies as to no
loss of exemption, and otherwise complies with the applicable requirements of the backup withholding rules. Non-U.S. Shareholders are generally exempt from information reporting and backup
withholding, but may be required to provide a properly completed Form&nbsp;W-8 or otherwise comply with applicable certification and identification procedures in order to prove their
exemption. Any amount paid as backup withholding will be creditable against the Non-U.S. Shareholder's United States income tax liability. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;U.S.
legislation enacted in 2010 (referred to as "FATCA") may impose withholding taxes on certain types of payments made to "foreign financial institutions" and certain other
non-U.S. entities. Under this legislation, the failure to comply with additional certification, information reporting and other specified requirements could result in the imposition of a
30% withholding tax on payments of dividends with respect to, and sales proceeds from the sale of, COPT's shares of beneficial interest paid to a foreign financial institution ("FFI") or to a foreign
entity other than a financial institution. Such withholding may apply unless (i)&nbsp;the FFI enters into an agreement with the United States Treasury and the Internal Revenue Service pursuant to
which the FFI will, among other things, perform certain diligence, reporting and withholding obligations with respect to certain of its owners/account holders, and separately, the FFI furnishes the
payor of such dividends and gross proceeds with all information and certifications required under Treasury regulations that implement FATCA or (ii)&nbsp;the foreign entity that is not an FFI either
certifies it does not have any substantial United States owners or furnishes identifying information regarding each substantial United States owner. Although the statutory rules generally apply to
payments made by an FFI made after December&nbsp;31, 2012, recently released IRS guidance (including proposed regulations) provides that FATCA withholding will be effective with respect to payments
of U.S. source dividends made after December&nbsp;31, 2013 (and after December&nbsp;31, 2014 with respect to payments of gross proceeds from the sale of securities giving rise to dividends). </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;FATCA
withholding tax may apply to dividends paid with respect to COPT's shares of beneficial interest, as well as gross proceeds from the sif the Fund cannot satisfy the applicable
requirements. In addition, in the event any amounts are withheld from payments made to the Fund pursuant to FATCA due to any failure by a U.S. Investor to provide information to the Fund necessary to
avoid such withholding, the Fund may collect the withheld taxes from such U.S. Investor (which, at the Fund's
discretion, may be collected from proceeds otherwise payable to the U.S. Investor from the redemption of Interests) and/or allocate or apportion to such U.S. Investor the withheld taxes. Each
prospective investor should consult with its own tax adviser as to the potential impact of FATCA in its own tax situation. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2><B> Other Tax Considerations  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Effect of Tax Status of the Operating Partnership on REIT Qualification.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;All of COPT's investments are through the Operating
Partnership. COPT
believes that the Operating Partnership is properly treated as a partnership for tax purposes (and not as an association taxable as a corporation). If, however, the Operating Partnership were to be
treated as an association taxable as a corporation, COPT would cease to qualify as a REIT. Furthermore, in such a situation, the Operating Partnership </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>30</FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>would
be subject to corporate income taxes and COPT would not be able to deduct its share of any losses generated by the Operating Partnership in computing its taxable income. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Tax Allocations with Respect to the Properties.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;The Operating Partnership was formed, in part, by way of contributions of appreciated
property. When
property is contributed to a partnership in exchange for an interest in the partnership, the partnership generally takes a carryover basis in that property for tax purposes equal to the adjusted basis
of the contributing partner in the property, rather than a basis equal to the fair market value of the property at the time of contribution (this difference is referred to as a "Book-Tax
Difference"). The partnership agreement of the Operating Partnership requires allocations of income, gain, loss and deduction with respect to contributed Property to be made in a manner consistent
with the special rules in Section&nbsp;704(c) of the Code, and the regulations thereunder, which tend to eliminate the Book-Tax Differences with respect to the contributed Properties
over the depreciable lives of the contributed Properties. However, because of certain technical limitations, the special allocation rules of Section&nbsp;704(c) may not always entirely eliminate the
Book-Tax Difference on an annual basis or with respect to a specific taxable transaction such as a sale. Thus, the carryover basis of the contributed properties in the hands of the
Operating Partnership could cause COPT to be allocated lower amounts of depreciation and other deductions for tax purposes than would be allocated to COPT if all properties were to have a tax
basis equal to their fair market value at the time of acquisition. The foregoing principles also apply in determining its earnings and profits for purposes of determining the portion of distributions
taxable as dividend income. The application of these rules over time may result in a higher portion of distributions being taxed as dividends than would have occurred had COPT purchased its interests
in all properties at their agreed value. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Treasury
Regulations under Section&nbsp;704(c) of the Code allow partnerships to use any reasonable method of accounting for Book-Tax Differences so that the contributing
partner receives the tax benefits and burdens of any built-in gain or loss associated with the property. The Operating Partnership has determined to use the "traditional method" (which is
specifically approved in the Treasury Regulations) for accounting for Book-Tax Differences with respect to the Contributed Properties. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Potential Impact of Taxable Stock Distributions on Shareholders.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;If COPT pays a dividend payable in cash or stock at the shareholder's
election, as
described above, taxable U.S. Shareholders will be required to include the full amount of the dividend as ordinary income to the extent of our accumulated earnings and profits. As a result, a U.S.
Shareholder's tax liability with respect to such dividend may exceed the cash portion of the dividend. If a U.S. Shareholder sells the shares that it receives as a dividend to pay this tax, the sales
proceeds may be less than the amount included in income with respect to the dividend, depending on the market price of our shares at the time of the sale. Furthermore, with respect to
Non-U.S. Shareholders, we may be required to withhold Federal tax with respect to such dividends, including in respect of all or a portion of such dividend payable in shares. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2><I> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Sunset of Beneficial Tax Rates.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;Several of the tax considerations described herein are subject to sunset clauses, which generally
provide that for
taxable years beginning after December&nbsp;31, 2012, certain provisions of the Code will revert back to earlier versions of such provisions. For instance, sunset clauses apply to provisions that
determine the maximum income tax rate applicable to taxpayers subject to tax at individual rates in respect of long-term capital gains (currently 15%, but previously 20%) and qualified
dividend income (currently 15%, but previously up to 39.6%). The impact of such reversions generally is not considered in this discussion, and current and prospective shareholders should consult with
their own tax advisors regarding the effect of such sunset clauses on an investment in COPT's shares of beneficial interest. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2><I>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;State and Local Taxes.</I></FONT><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;COPT and its shareholders may be subject to state or local taxation in various state or local jurisdictions,
including those
in which COPT or they transact business or reside. </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>The
state and local tax treatment of us and its shareholders may not conform to the federal income tax consequences discussed above. Consequently, prospective shareholders should consult with their
own tax advisors regarding the effect of state, local and other tax laws of any investment in COPT's shares of beneficial interest. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Plan"></A>PLAN OF DISTRIBUTION  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Unless otherwise set forth in a prospectus supplement accompanying this prospectus, we may sell the securities offered pursuant to this
prospectus to or through one or more underwriters or dealers, or we may sell the securities to investors directly or through agents. Any such underwriter, dealer or agent involved in the offer and
sale of the securities will be named in the applicable prospectus supplement. We may sell securities directly to investors on our own behalf in those jurisdictions where we are authorized to do so. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Underwriters
may offer and sell the securities at a fixed price or prices which may be changed, at market prices prevailing at the time of sale, at prices related to such prevailing
market prices or at negotiated prices. We also may, from time to time, authorize dealers or agents to offer and sell the securities upon such terms and conditions as may be set forth in the applicable
prospectus supplement. In connection with the sale of any of the securities, underwriters may receive compensation from us in the form of underwriting discounts or commissions and may also receive
commissions from purchasers of the securities for whom they may act as agent. Underwriters may sell the securities to or through dealers, and such dealers may receive compensation in the form of
discounts, concessions or commissions from the underwriters or commissions from the purchasers for whom they may act as agents. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
common shares may also be sold in one or more of the following transactions: (a)&nbsp;block transactions (which may involve crosses) in which a broker-dealer may sell all or a
portion of such shares as agent, but may position and resell all or a portion of the block as principal to facilitate the transaction; (b)&nbsp;purchases by any such broker-dealer as principal, and
resale by such broker-dealer for its own account pursuant to a prospectus supplement; (c)&nbsp;a special offering, an exchange distribution or a secondary distribution in accordance with applicable
New York Stock Exchange or other stock exchange, quotation system or over-the-counter market rules; (d)&nbsp;ordinary brokerage transactions and transactions in which any
such broker-dealer solicits purchasers; (e)&nbsp;sales "at the market" to or through a market maker or into an existing trading market, on an exchange or otherwise, for such shares; and
(f)&nbsp;sales in other ways not involving market makers or established trading markets, including direct sales to purchasers. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Any
underwriting compensation paid by us to underwriters or agents in connection with the offering of the securities, and any discounts or concessions or commissions allowed by
underwriters to participating dealers, will be set forth in the applicable prospectus supplement. Dealers and agents participating in the distribution of the securities may be deemed to be
underwriters, and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions. </FONT></P>


<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Underwriters,
dealers and agents may be entitled, under agreements entered into with us, to indemnification against and contribution toward certain civil liabilities, including
liabilities under the Securities Act of 1933, as amended. Unless otherwise set forth in an accompanying prospectus supplement, the obligations of any underwriters to purchase any of the securities
will be subject to certain conditions precedent, and the underwriters will be obligated to purchase all of such securities, if any are purchased. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Underwriters,
dealers and agents may engage in transactions with, or perform services for, us and our affiliates in the ordinary course of business. </FONT></P>

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<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If indicated in the prospectus supplement, we may authorize underwriters or other agents to solicit offers by institutions to purchase securities from us pursuant
to contracts providing for payment and delivery on a future date. Institutions with which we may make these delayed delivery contracts include commercial and savings banks, insurance companies,
pension funds, investment companies, educational and charitable institutions and others. The obligations of any purchaser under any such delayed delivery contract will be subject to the condition that
the purchase of the securities shall not at the time of delivery be prohibited under the laws of the jurisdiction to which the purchaser is subject. The underwriters and other agents will not have any
responsibility with regard to the validity or performance of these delayed delivery contracts. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
connection with the offering of the securities hereby, certain underwriters, and selling group members and their respective affiliates may engage in transactions that stabilize,
maintain or otherwise affect the market price of the applicable securities. Such transactions may include stabilization transactions effected in accordance with Rule&nbsp;104 of Regulation&nbsp;M
promulgated by the SEC pursuant to which such persons may bid for or purchase securities for the purpose of stabilizing their market price. The underwriters in an offering of securities may also
create a "short position" for their account by selling more securities in connection with the offering than they are committed to purchase from us. In such case, the underwriters could cover all or a
portion of such short position by either purchasing securities in the open market following completion of the offering of such securities or by exercising any over-allotment option granted
to them by us. In addition, the managing underwriter may impose "penalty bids" under contractual arrangements with other underwriters, which means that they can reclaim from an underwriter (or any
selling group member participating in the offering) for the account of the other underwriters, the selling concession with respect to securities that are
distributed in the offering but subsequently purchased for the account of the underwriters in the open market. Any of the transactions described in this paragraph or comparable transactions that are
described in any accompanying prospectus supplement may result in the maintenance of the price of the securities at a level above that which might otherwise prevail in the open market. None of such
transactions described in this paragraph or in an accompanying prospectus supplement are required to be taken by any underwriters and, if they are undertaken, may be discontinued at any time. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Our
common shares are listed on the New York Stock Exchange under the symbol "OFC." Any new series of preferred shares or warrants will be new issues of securities with no established
trading market and may or may not be listed on a national securities exchange, quotation system or over-the-counter market. Any underwriters or agents to or through which
securities are sold by us may make a market in such securities, but such underwriters or agents will not be obligated to do so and any of them may discontinue any market making at any time without
notice. No assurance can be given as to the liquidity of or trading market for any securities sold by us. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Expert"></A>EXPERTS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The financial statements and management's assessment of the effectiveness of internal control over financial reporting (which is
included in Management's Report on Internal Control Over Financing Reporting) incorporated in this prospectus by reference to our Annual Report on Form&nbsp;10-K for the year ended
December&nbsp;31, 2011 have been so incorporated in reliance on the report of PricewaterhouseCoopers&nbsp;LLP, an independent registered public accounting firm, given on the authority of said firm
as experts in auditing and accounting. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Sell_sec"></A>SELLING SECURITYHOLDERS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Information about selling securityholders, where applicable, will be set forth in a prospectus supplement, in a
post-effective amendment, or in filings we make with the SEC under the Securities Exchange Act of 1934 which are incorporated by reference. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>33</FONT></P>

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<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Leg_Mtr"></A>LEGAL MATTERS  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The validity of the securities offered hereby is being passed upon for us by Saul Ewing&nbsp;LLP. The opinion of counsel as described
under the heading "Federal Income Tax Matters" is being rendered by Morgan, Lewis&nbsp;&amp; Bockius&nbsp;LLP, which opinion is subject to various assumptions and is based on current tax law. Certain
legal matters may be passed upon for any of the underwriters or agents by counsel named in the applicable prospectus supplement. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> <A NAME="Where"></A>WHERE YOU CAN FIND MORE INFORMATION  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We have filed a registration statement on Form&nbsp;S-3 with the Securities and Exchange Commission in connection with
this offering. In addition, we file annual, quarterly, and current reports, proxy statements and other information with the Securities and Exchange Commission. You may read and copy the registration
statement and any other documents filed by us at the Securities and Exchange Commission's Public Reference Room at 100&nbsp;F Street, N.E., Washington, D.C. 20549. Please call the Securities and
Exchange Commission at 1-800-SEC-0330 for further information on the Public Reference Room. Our Securities and Exchange Commission filings are also available to the
public at the Securities and Exchange Commission's Internet site at http://www.sec.gov. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This
prospectus is part of the registration statement and does not contain all of the information included in the registration statement. If a reference is made in this prospectus or any
prospectus supplement to any of our contracts or other documents, the reference may not be complete and you should refer to the exhibits that are a part of the registration statement for a copy of the
contract or document. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The
Securities and Exchange Commission allows us to "incorporate by reference" into this prospectus the information we file with the Commission, which means that we can disclose
important information to you by referring you to those documents. Information incorporated by reference is part of this prospectus. Later information filed with the Securities and Exchange Commission
will update and supersede this information. </FONT></P>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;We
incorporate by reference the documents listed below and any future filings we make with the Securities and Exchange Commission under Sections&nbsp;13(a), 13(c), 14 or 15(d) of the
Exchange Act until this offering is completed:</FONT></P>

<UL>
<DL compact>
<DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>Annual Report on Form&nbsp;10-K for the year ended December&nbsp;31, 2011; </FONT> <FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>Current Reports on Form&nbsp;8-K, filed with the Securities and Exchange Commission on February&nbsp;16,
2012 and March&nbsp;9, 2012; </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>Definitive Proxy Statement for the 2012 Annual Meeting of Shareholders, filed with the Securities and Exchange Commission
on March&nbsp;29, 2012; and </FONT><FONT SIZE=2>
<BR><BR></FONT></DD><DT style='font-family:times;margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD style="font-family:times;"><FONT SIZE=2>Registration Statement on Form&nbsp;8-A relating to the registration of our common shares, filed with the
Securities and Exchange Commission on April&nbsp;7, 1998. </FONT></DD></DL>
</UL>

<P style="font-family:times;"><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;You
may request a copy of these filings, at no cost, by contacting Investor Relations, Corporate Office Properties Trust, 6711 Columbia Gateway Drive, Suite&nbsp;300, Columbia,
Maryland 21046, by telephone at 443-285-5400, by facsimile at 443-285-7640, or by e-mail at ir@copt.com, or by visiting our website at
www.copt.com. The information contained on our website is not part of this prospectus. Our reference to our website is intended to be an inactive textual reference only. </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2>34</FONT></P>

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<A HREF="#bg11001a_main_toc">Table of Contents</A> </FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B>
<IMG SRC="g694461.jpg" ALT="GRAPHIC" WIDTH="226" HEIGHT="130">
  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B>7,500,000 Shares  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> Common Shares of Beneficial Interest  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B>PROSPECTUS SUPPLEMENT  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=2><B> October&nbsp;11, 2012  </B></FONT></P>

<P style="font-family:times;"><FONT SIZE=2><B>

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<HR NOSHADE  COLOR="#000000" SIZE="1.0PT" WIDTH="100%" ALIGN="LEFT" >


 </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B>Wells Fargo Securities  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> J.P. Morgan  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> Barclays  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> KeyBanc Capital Markets  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> Piper Jaffray  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> RBC Capital Markets  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> Baird  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> Comerica Securities  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> PNC Capital Markets&nbsp;LLC  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> Stifel Nicolaus Weisel  </B></FONT></P>

<P ALIGN="CENTER" style="font-family:times;"><FONT SIZE=4><B> SunTrust Robinson Humphrey  </B></FONT></P>

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<P style='font-family:times;page-break-before:always'></p>
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`
end
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
