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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>0001104659-09-061966.txt : 20091102
<SEC-HEADER>0001104659-09-061966.hdr.sgml : 20091102
<ACCEPTANCE-DATETIME>20091102211759
ACCESSION NUMBER:		0001104659-09-061966
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20091102
FILED AS OF DATE:		20091102
DATE AS OF CHANGE:		20091102

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			COWEN GROUP, INC.
		CENTRAL INDEX KEY:			0001466538
		STANDARD INDUSTRIAL CLASSIFICATION:	SECURITY BROKERS, DEALERS & FLOTATION COMPANIES [6211]
		IRS NUMBER:				000000000

	BUSINESS ADDRESS:	
		STREET 1:		1221 AVENUE OF THE AMERICAS
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10020
		BUSINESS PHONE:		(646) 562-1000

	MAIL ADDRESS:	
		STREET 1:		1221 AVENUE OF THE AMERICAS
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10020

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	LexingtonPark Parent Corp
		DATE OF NAME CHANGE:	20090617

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			STARK MORGAN B
		CENTRAL INDEX KEY:			0001267535

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34516
		FILM NUMBER:		091152538

	MAIL ADDRESS:	
		STREET 1:		C/O RAMIUS LLC
		STREET 2:		599 LEXINGTON AVENUE 20TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>a4.xml
<DESCRIPTION>4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-11-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001466538</issuerCik>
        <issuerName>COWEN GROUP, INC.</issuerName>
        <issuerTradingSymbol>COWN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001267535</rptOwnerCik>
            <rptOwnerName>STARK MORGAN B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O COWEN GROUP, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>599 LEXINGTON AVENUE</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO/President of Ramius LLC</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2009-11-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2435132</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2435132</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Upon consummation of the transactions (the &quot;Transactions&quot;) contemplated by the Transaction Agreement and Agreement and Plan of Merger, dated as of June 3, 2009, by and among Cowen Holdings, Inc. (f/k/a Cowen Group, Inc.), Cowen Group, Inc. (f/k/a/ LexingtonPark Parent Corp.), Lexington Merger Corp., Ramius LLC (f/k/a Park Exchange LLC) and RCG Holdings LLC (f/k/a Ramius LLC) (&quot;RCG&quot;), 37,536,826 shares of Class A Common Stock were issued to RCG.  The Reporting Person is a member of RCG and may be deemed to have a pecuniary interest in 2,435,132 shares of Class A Common Stock that were acquired by RCG in the Transactions, including 2,376,924 shares that are held by RCG and allocated to the Reporting Person in connection with his ownership interest in RCG and 58,208 shares that are held by RCG and allocated to the Reporting Person's wife in connection with her ownership interest in RCG.</footnote>
        <footnote id="F2">The Reporting Person's acquisition of a pecuniary interest in these shares was pursuant to an exempt transaction pursuant to Rule 16b-3 under the Securities Exchange Act of 1934, as amended.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Morgan B. Stark</signatureName>
        <signatureDate>2009-11-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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