-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0001179477-05-000016.txt : 20050615
<SEC-HEADER>0001179477-05-000016.hdr.sgml : 20050614
<ACCEPTANCE-DATETIME>20050615121525
ACCESSION NUMBER:		0001179477-05-000016
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050613
FILED AS OF DATE:		20050615
DATE AS OF CHANGE:		20050615

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			QUESTAR CORP
		CENTRAL INDEX KEY:			0000751652
		STANDARD INDUSTRIAL CLASSIFICATION:	CRUDE PETROLEUM & NATURAL GAS [1311]
		IRS NUMBER:				870407509
		STATE OF INCORPORATION:			UT
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		180 EAST 100 SOUTH ST
		STREET 2:		PO BOX 45433
		CITY:			SALT LAKE CITY
		STATE:			UT
		ZIP:			84145
		BUSINESS PHONE:		8015345000

	MAIL ADDRESS:	
		STREET 1:		180 EAST 100 SOUTH ST
		STREET 2:		P O BOX 45433
		CITY:			SALT LAKE CITY
		STATE:			UT
		ZIP:			84145

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CASH R D
		CENTRAL INDEX KEY:			0001179477

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-08796
		FILM NUMBER:		05896877

	BUSINESS ADDRESS:	
		STREET 1:		180 EAST 100 SOUTH
		STREET 2:		PO BOX 45433
		CITY:			SALT LAKE CITY
		STATE:			UT
		ZIP:			84145-0433
		BUSINESS PHONE:		8013245205

	MAIL ADDRESS:	
		STREET 1:		3205 61ST STREET
		CITY:			LUBBOCK
		STATE:			TX
		ZIP:			79413
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-06-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000751652</issuerCik>
        <issuerName>QUESTAR CORP</issuerName>
        <issuerTradingSymbol>STR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001179477</rptOwnerCik>
            <rptOwnerName>CASH R D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>3205 61ST STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LUBBOCK</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>79413</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock and attached Common Stock Purchase Rights</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>313517</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock and attached Common Stock Purchase Rights</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>37043</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Private Foundation</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>64.28</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-06-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>27.3186</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>64.28</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Phantom Stock Units</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>27.3186</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5713.9934</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>64.28</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-06-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10.6582</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>64.28</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Phantom Stock Units</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10.6582</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>15591.1521</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeHolding>
            <securityTitle>
                <value>Common Stock and attached Common Stock Purchase Rights</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F5"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock and attached Common Stock Purchase Rights</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>485858</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This total does not include 7,534 shares held indirectly through family trusts for which I have voting and investment control.  I have a power of attorney for 6,000 shares owned by father for which I have investment and voting control.  I disclaim any economic interest in these shares or in the shares held through family trusts.</footnote>
        <footnote id="F2">May 1, 2004-2006.</footnote>
        <footnote id="F3">I have account balances in several deferred compensation plans for directors.  Such account balances are credited with dividends.  I began receiving annual cash payments for the value of my phantom stock units attributable to deferred director's fees effective June 1, 2004.</footnote>
        <footnote id="F4">This total includes 12,535.5778 phantom stock units held in an excess benefits plan.  I began receiving cash payments for the value of phantom stock units (exclusive of deferral director's fees) effective May 1, 2003.</footnote>
        <footnote id="F5">The question about dates is irrelevant since I am not reporting any changes in my stock options.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Abigail L. Jones Attorney in Fact for R.D. Cash</signatureName>
        <signatureDate>2005-06-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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