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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-05-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000912752</issuerCik>
        <issuerName>SINCLAIR BROADCAST GROUP INC</issuerName>
        <issuerTradingSymbol>SBGI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001016817</rptOwnerCik>
            <rptOwnerName>SMITH DAVID D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O SINCLAIR BROADCAST GROUP</rptOwnerStreet1>
            <rptOwnerStreet2>10706 BEAVER DAM ROAD</rptOwnerStreet2>
            <rptOwnerCity>COCKEYSVILLE</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>21030</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Chairman</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-05-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1200</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>30.5234</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>162553</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Sole voting member of limited liability company</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The Reporting Person also directly owns (i) 119,592 shares of Class A Common Stock, (ii) 11,539.68804 shares of Class A Common Stock held in a 401(k) unitized stock fund, (iii) 134,172 shares of Class A Common Stock issued as Restricted Stock and (iv) 6,211,072.227 shares of Class B Common Stock.  The Reporting Person also indirectly owns (i) 28,160 shares of Class A Common Stock held in separate custodial accounts established by the Reporting Person for the benefit of family members of which the Reporting Person is the custodian, (ii) 338,400 shares of Class A Common Stock held by trusts f/b/o family members of which the Reporting Person is a trustee, (iii) 354,000 shares of Class A Common Stock held f/b/o David D. Smith Foundation, Inc., which the Reporting Person controls, but does not derive any benefit, and (iv) 1,000,000 shares of Class B Common Stock held by trusts f/b/o family members.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Clinton R. Black, V, Esq., on behalf of David D. Smith, by Power of Attorney</signatureName>
        <signatureDate>2019-03-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
