<?xml version="1.0"?><ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-08-04</periodOfReport><notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000075129</issuerCik>
        <issuerName>OTTER TAIL CORP</issuerName>
        <issuerTradingSymbol>OTTR</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001191493</rptOwnerCik>
            <rptOwnerName>KOECK GEORGE A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>215 S CASCADE ST</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>FERGUS FALLS</rptOwnerCity>
            <rptOwnerState>MN</rptOwnerState>
            <rptOwnerZipCode>56537-2801</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Corp Secretary &amp; Gen Counsel</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-08-04</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>F</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>140</value></transactionShares><transactionPricePerShare><value>25.93</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>10558</value><footnoteId id="F1" /></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></nonDerivativeTransaction></nonDerivativeTable><footnotes><footnote id="F1">The Corporation's Stock Incentive Plan, which is a grant of Restricted Stock.  The grant price for 8/2/99 was $43.50, vesting 20% yearly.  On 8/4/03, 140 shares were withheld by the Corporation to pay taxes due upon vesting of restricted stock, exempt pursuant to Rule 16b-3(e).  458 shares remain restricted, with 1,840 shares lifted from the restriction.
The grant price for 4/8/02 was $31.34 vesting 25% yearly with 3,900 shares holding the restriction.
The grant price for 4/14/03 was $27.245 vesting 25% yearly with 6,200 shares holding the restriction.
See below for other holdings:
1.  Indirect holding of 611.3265 shares held by ESOP.
2.  Direct holding of 1,383.2522 shares held in the Dividend Reinvestment Plan.
3.  Direct holding of 320 shares which no longer carries the restriction.
4.  2,500 stock options with expiration date of 8/2/2009.
5.  4,125 stock options with expiration date of 4/9/2010.
6.  20,000 stock options with expiration date of 4/8/2011.</footnote></footnotes><remarks></remarks><ownerSignature><signatureName>/s/ George A Koeck by Debra J Lill - POA</signatureName><signatureDate>2003-08-05</signatureDate></ownerSignature></ownershipDocument>

