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<!-- RR Donnelley Xcelerate Taxonomy Schema, based on XBRL 2.1  http://www.rrdonnelley.com/ -->
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<!-- Creation date: 2012-11-08T01:51:52Z -->
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  <element name="RatioOfTotalOutstandingBorrowingToBorrowingBaseAxis" id="oas_RatioOfTotalOutstandingBorrowingToBorrowingBaseAxis" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:dimensionItem"/>
  <element name="ReconciliationOfBasicWeightedAverageSharesToDilutedWeightedAverageSharesTable" id="oas_ReconciliationOfBasicWeightedAverageSharesToDilutedWeightedAverageSharesTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="RedemptionPercentageMaximum" id="oas_RedemptionPercentageMaximum" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RevenuesPayableAndProductionTaxesCurrent" id="oas_RevenuesPayableAndProductionTaxesCurrent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfCondensedConsolidatingBalanceSheetTableTextBlock" id="oas_ScheduleOfCondensedConsolidatingBalanceSheetTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfCondensedConsolidatingStatementOfCashFlowsTableTextBlock" id="oas_ScheduleOfCondensedConsolidatingStatementOfCashFlowsTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfCondensedConsolidatingStatementOfOperationsTableTextBlock" id="oas_ScheduleOfCondensedConsolidatingStatementOfOperationsTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfOtherThanOptionsLineItems" id="oas_ScheduleOfOtherThanOptionsLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfOtherThanOptionsTable" id="oas_ScheduleOfOtherThanOptionsTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsPerformancePeriod" id="oas_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsPerformancePeriod" type="xbrli:positiveIntegerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueAmortizationPeriod" id="oas_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueAmortizationPeriod" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationOtherThanOptionAxis" id="oas_ShareBasedCompensationOtherThanOptionAxis" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:dimensionItem"/>
  <element name="ShareBasedCompensationOtherThanOptionDomain" id="oas_ShareBasedCompensationOtherThanOptionDomain" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TreasuryStockAtCost" id="oas_TreasuryStockAtCost" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TreasuryStockCost" id="oas_TreasuryStockCost" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TreasuryStockWithheldMember" id="oas_TreasuryStockWithheldMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandFifteenThreeWayCollarsMember" id="oas_TwoThousandFifteenThreeWayCollarsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandFourteenPutSpreadsMember" id="oas_TwoThousandFourteenPutSpreadsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandFourteenSwapContractsMember" id="oas_TwoThousandFourteenSwapContractsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandFourteenThreeWayCollarsMember" id="oas_TwoThousandFourteenThreeWayCollarsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandFourteenTwoWayAndThreeWayCollarsMember" id="oas_TwoThousandFourteenTwoWayAndThreeWayCollarsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandFourteenTwoWayCollarsMember" id="oas_TwoThousandFourteenTwoWayCollarsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandNineteenNotesMember" id="oas_TwoThousandNineteenNotesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandThirteenPutSpreadsMember" id="oas_TwoThousandThirteenPutSpreadsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandThirteenSwapContractsMember" id="oas_TwoThousandThirteenSwapContractsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandThirteenThreeWayCollarsMember" id="oas_TwoThousandThirteenThreeWayCollarsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandThirteenTwoWayAndThreeWayCollarsMember" id="oas_TwoThousandThirteenTwoWayAndThreeWayCollarsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandThirteenTwoWayCollarsMember" id="oas_TwoThousandThirteenTwoWayCollarsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandTwelveSwapContractsMember" id="oas_TwoThousandTwelveSwapContractsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandTwelveThreeWayCollarsMember" id="oas_TwoThousandTwelveThreeWayCollarsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandTwelveTwoWayAndThreeWayCollarsMember" id="oas_TwoThousandTwelveTwoWayAndThreeWayCollarsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandTwelveTwoWayCollarsMember" id="oas_TwoThousandTwelveTwoWayCollarsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandTwentyOneAndTwoThousandNineteenNotesMember" id="oas_TwoThousandTwentyOneAndTwoThousandNineteenNotesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandTwentyOneNotesMember" id="oas_TwoThousandTwentyOneNotesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandTwentyThreeNotesMember" id="oas_TwoThousandTwentyThreeNotesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UnprovedOilAndGasPropertiesMember" id="oas_UnprovedOilAndGasPropertiesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UnsecuredSeniorNotesMember" id="oas_UnsecuredSeniorNotesMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="WeightedAverageNumberOfSharesOutstandingReconciliationLineItems" id="oas_WeightedAverageNumberOfSharesOutstandingReconciliationLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="WillistonBasinProjectMember" id="oas_WillistonBasinProjectMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
</schema>
