<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2011-05-12</periodOfReport>

    <issuer>
        <issuerCik>0001004980</issuerCik>
        <issuerName>PG&amp;E CORP</issuerName>
        <issuerTradingSymbol>PCG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001221221</rptOwnerCik>
            <rptOwnerName>RAMBO BARBARA L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O PG&amp;E CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>ONE MARKET, SPEAR TOWER, SUITE 2400</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94105</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2011-05-12</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1934</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14685</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Restricted Stock Units (RSUs) granted under the PG&amp;E Corporation 2006 Long-Term Incentive Plan (LTIP).  RSUs are payable in shares of PG&amp;E Corporation common stock on a one-for-one basis upon the earliest of one year from the date of grant, a director's death, disability, retirement, or a change in control, as defined in the LTIP.</footnote>
        <footnote id="F2">This total includes 1,144.37 units of phantom stock granted under the PG&amp;E Corporation Non-Employee Director Stock Incentive Plan (SIP), and reflects the acquisition of 11.57 units of phantom stock on 4/15/10, 11.49 units of phantom stock on 7/15/10, 10.78 units of phantom stock on 10/15/10, 10.78 units of phantom stock on 1/18/11, and 11.49 units of phantom stock on 4/15/11, pursuant to a dividend reinvestment feature of the SIP.  This total also includes 7,611.60 RSUs granted under the LTIP, and reflects the acquisition of 57.40 RSUs on 4/15/10, 57.05 RSUs on 7/15/10, 53.49 RSUs on 10/15/10, 53.48 RSUs on 1/18/11, and 57.01 RSUs on 4/15/11 pursuant to a dividend reinvestment feature of the LTIP.  The phantom stock units and the RSUs are automatically payable in shares of PG&amp;E Corporation common stock only.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Eric A. Montizambert, attorney-in-fact for Barbara L. Rambo (signed Power of Attorney on file with SEC)</signatureName>
        <signatureDate>2011-05-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
