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  <xs:element id="onl_NumberOfRealEstatePropertiesToBeSoldAndSubsequentlyTerminated" abstract="false" name="NumberOfRealEstatePropertiesToBeSoldAndSubsequentlyTerminated" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="onl_RightOfUseAssetNet" abstract="false" name="RightOfUseAssetNet" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_BelowMarketLeaseRightOfUseAsset" abstract="false" name="BelowMarketLeaseRightOfUseAsset" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_InterestRateCollarMember" abstract="true" name="InterestRateCollarMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_MeasurementInputEstimatedSalesPriceUnderDefinitiveAgreementsMember" abstract="true" name="MeasurementInputEstimatedSalesPriceUnderDefinitiveAgreementsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_MeasurementInputEstimatedSalesPriceOnMarketDataMember" abstract="true" name="MeasurementInputEstimatedSalesPriceOnMarketDataMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_NumberOfImpairedProperties" abstract="false" name="NumberOfImpairedProperties" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="onl_MeasurementInputRealEstateImpairment" abstract="false" name="MeasurementInputRealEstateImpairment" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:decimalItemType"/>
  <xs:element id="onl_CarryingValueOfImpairedProperties" abstract="false" name="CarryingValueOfImpairedProperties" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_ImpairedRealEstatePropertiesFairValue" abstract="false" name="ImpairedRealEstatePropertiesFairValue" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_DebtRollForward" abstract="true" name="DebtRollForward" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="onl_DebtLongTermAndShortTermGrossCombinedAmount" abstract="false" name="DebtLongTermAndShortTermGrossCombinedAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_RepaymentsExtinguishmentAndAssumptionsOfDebtNet" abstract="false" name="RepaymentsExtinguishmentAndAssumptionsOfDebtNet" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_OrionOperatingPartnershipMember" abstract="true" name="OrionOperatingPartnershipMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_InterestRateCollarInstrumentOneMember" abstract="true" name="InterestRateCollarInstrumentOneMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_InterestRateCollarInstrumentTwoMember" abstract="true" name="InterestRateCollarInstrumentTwoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_InterestRateCollarInstrumentThreeMember" abstract="true" name="InterestRateCollarInstrumentThreeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_DebtInstrumentTermNumberOfExtensionOptions" abstract="false" name="DebtInstrumentTermNumberOfExtensionOptions" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="onl_DebtInstrumentTermExtensionPeriod" abstract="false" name="DebtInstrumentTermExtensionPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="onl_DebtInstrumentInterestRateVariableRateBasisPointAdjustment" abstract="false" name="DebtInstrumentInterestRateVariableRateBasisPointAdjustment" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="onl_NumberOfPropertiesPledgedAsCollateral" abstract="false" name="NumberOfPropertiesPledgedAsCollateral" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="onl_DebtInstrumentPercentageOfNetCashProceedsForRepaymentOfDebt" abstract="false" name="DebtInstrumentPercentageOfNetCashProceedsForRepaymentOfDebt" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="onl_DebtInstrumentCovenantUnrestrictedCashAndCashEquivalents" abstract="false" name="DebtInstrumentCovenantUnrestrictedCashAndCashEquivalents" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_DebtInstrumentCovenantTotalDebtToTotalAssetValueMaximum" abstract="false" name="DebtInstrumentCovenantTotalDebtToTotalAssetValueMaximum" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="onl_DebtInstrumentCovenantEBITDAToFixedChargesMinimum" abstract="false" name="DebtInstrumentCovenantEBITDAToFixedChargesMinimum" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="onl_DebtInstrumentCovenantNetWorthRequirementMinimum" abstract="false" name="DebtInstrumentCovenantNetWorthRequirementMinimum" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_DebtInstrumentCovenantNetProceedsFromEquityOffering" abstract="false" name="DebtInstrumentCovenantNetProceedsFromEquityOffering" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="onl_DebtInstrumentCovenantCollateralPropertyMinimumAmount" abstract="false" name="DebtInstrumentCovenantCollateralPropertyMinimumAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_DebtInstrumentCovenantCollateralPropertyAppraisedValue" abstract="false" name="DebtInstrumentCovenantCollateralPropertyAppraisedValue" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="onl_DebtInstrumentCovenantCollateralPropertyDebtYield" abstract="false" name="DebtInstrumentCovenantCollateralPropertyDebtYield" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="onl_NumberOfRealEstatePropertiesUsedToSecureDebt" abstract="false" name="NumberOfRealEstatePropertiesUsedToSecureDebt" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="onl_NumberOfRealEstatePropertiesSold" abstract="false" name="NumberOfRealEstatePropertiesSold" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="onl_DebtInstrumentCovenantLiquidAssetRequirementMinimum" abstract="false" name="DebtInstrumentCovenantLiquidAssetRequirementMinimum" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_DebtInstrumentPrepaymentPeriodAxis" abstract="true" name="DebtInstrumentPrepaymentPeriodAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="onl_DebtInstrumentPrepaymentPeriodDomain" abstract="true" name="DebtInstrumentPrepaymentPeriodDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_OneYearExtensionPeriodMember" abstract="true" name="OneYearExtensionPeriodMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_SixMonthsExtensionPeriodMember" abstract="true" name="SixMonthsExtensionPeriodMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_DebtInstrumentMaturityDateExtension" abstract="false" name="DebtInstrumentMaturityDateExtension" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="onl_DebtInstrumentPrepaymentOfPrincipalAmount" abstract="false" name="DebtInstrumentPrepaymentOfPrincipalAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_DebtInstrumentPartialPrepaymentAmount" abstract="false" name="DebtInstrumentPartialPrepaymentAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_DebtInstrumentPrepaymentOfAdditionalPrincipalAmountPercent" abstract="false" name="DebtInstrumentPrepaymentOfAdditionalPrincipalAmountPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="onl_DebtInstrumentPrepaymentOfRemainingPrincipalAmountPercent" abstract="false" name="DebtInstrumentPrepaymentOfRemainingPrincipalAmountPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="onl_LoanReservesSubjectToCapAmount" abstract="false" name="LoanReservesSubjectToCapAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_SanRamonLoanMember" abstract="true" name="SanRamonLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_VariableRateDebtMember" abstract="true" name="VariableRateDebtMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_DerivativeAssetLiabilityOffsettingAmountFairValueGross" abstract="false" name="DerivativeAssetLiabilityOffsettingAmountFairValueGross" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_DerivativeFinancialInstruments" abstract="false" name="DerivativeFinancialInstruments" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_SupplementalCashFlowDisclosuresAbstract" abstract="true" name="SupplementalCashFlowDisclosuresAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="onl_EstablishmentOfRightOfUseAssetsAndLeaseLiabilities" abstract="false" name="EstablishmentOfRightOfUseAssetsAndLeaseLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_LandRightOfUseAssetAcquired" abstract="false" name="LandRightOfUseAssetAcquired" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_AccruedCapitalExpendituresAndLeasingCosts" abstract="false" name="AccruedCapitalExpendituresAndLeasingCosts" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_LessorOperatingLeaseCommitmentOutstandingTenantImprovementAllowance" abstract="false" name="LessorOperatingLeaseCommitmentOutstandingTenantImprovementAllowance" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_LessorOperatingLeaseCommitmentOutstandingReimbursableLandlordWork" abstract="false" name="LessorOperatingLeaseCommitmentOutstandingReimbursableLandlordWork" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_LessorOperatingLeaseCommitmentOutstandingNonReimbursableLandlordWork" abstract="false" name="LessorOperatingLeaseCommitmentOutstandingNonReimbursableLandlordWork" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_LessorOperatingLeaseCommitmentOutstanding" abstract="false" name="LessorOperatingLeaseCommitmentOutstanding" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_LessorOperatingLeaseRestrictedCashIncludedInCommitmentOutstanding" abstract="false" name="LessorOperatingLeaseRestrictedCashIncludedInCommitmentOutstanding" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_AmortizationReversalOfLeaseIntangiblesNet" abstract="false" name="AmortizationReversalOfLeaseIntangiblesNet" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_OperatingLeaseFixedLeaseIncomeReimbursements" abstract="false" name="OperatingLeaseFixedLeaseIncomeReimbursements" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_OperatingLeaseOtherFixedRentalRevenue" abstract="false" name="OperatingLeaseOtherFixedRentalRevenue" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_OperatingLeaseFixedLeaseIncome" abstract="false" name="OperatingLeaseFixedLeaseIncome" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_OperatingLeaseVariableLeaseIncomeReimbursements" abstract="false" name="OperatingLeaseVariableLeaseIncomeReimbursements" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_OperatingLeaseVariableLeaseIncomeOtherRentalRevenue" abstract="false" name="OperatingLeaseVariableLeaseIncomeOtherRentalRevenue" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_OperatingLeasePaymentsCapitalized" abstract="false" name="OperatingLeasePaymentsCapitalized" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="onl_RealtyIncomeMember" abstract="true" name="RealtyIncomeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_NumberOfCompanySharesOwnedByRelatedParty" abstract="false" name="NumberOfCompanySharesOwnedByRelatedParty" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="onl_TimeBasedRestrictedStockUnitsAndRestrictedStockUnitsMember" abstract="true" name="TimeBasedRestrictedStockUnitsAndRestrictedStockUnitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_PerformanceBasedRestrictedStockUnitsMember" abstract="true" name="PerformanceBasedRestrictedStockUnitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_MetricBasedRestrictedStockUnitsMember" abstract="true" name="MetricBasedRestrictedStockUnitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_TimeBasedRestrictedStockUnitsAndPerformanceBasedRestrictedStockUnitsMember" abstract="true" name="TimeBasedRestrictedStockUnitsAndPerformanceBasedRestrictedStockUnitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_PlanoTexasMember" abstract="true" name="PlanoTexasMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_TulsaOklahomaMember" abstract="true" name="TulsaOklahomaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="onl_SalemOregonMember" abstract="true" name="SalemOregonMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
