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Baron Capital Group, Inc., BAMCO, Inc., Baron Capital Management, Inc. and Ronald Baron report a significant ownership stake in CoStar Group, Inc. They collectively report beneficial ownership of 21,626,763 shares of CoStar common stock, representing 5.3% of the outstanding class as of June 30, 2026.
All reported shares are held with shared rather than sole power. The group reports 21,369,752 shares with shared voting power and 21,626,763 shares with shared dispositive power, with no sole voting or dispositive power. BAMCO and Baron Capital Management are subsidiaries of Baron Capital Group, and Ronald Baron owns a controlling interest in Baron Capital Group.
The advisory clients of BAMCO and Baron Capital Management have the right to receive dividends or sale proceeds for the CoStar shares held in their accounts, and to the filers’ knowledge, no single client has an interest in more than 5% of the class.
Key Figures
Shares beneficially owned:21,626,763 sharesPercent of class owned:5.3 %Shared voting power:21,369,752 shares+3 more
6 metrics
Shares beneficially owned21,626,763 sharesCommon stock of CoStar Group, Inc. beneficially owned by the Baron group
Percent of class owned5.3 %Portion of CoStar Group common stock outstanding held by the Baron group
Shared voting power21,369,752 sharesShares of CoStar Group for which the Baron group has shared voting power
Shared dispositive power21,626,763 sharesShares of CoStar Group for which the Baron group has shared power to dispose
CUSIP22160N109CUSIP number for CoStar Group, Inc. common stock
Reporting date06/30/2026Date as of which ownership in CoStar Group is reported
Key Terms
beneficially owned, shared voting power, shared dispositive power, Investment Company Act of 1940, +1 more
5 terms
beneficially ownedfinancial
"Amount beneficially owned: 21,626,763"
Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.
shared voting powerfinancial
"Shared Voting Power 21,369,752.00"
Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.
shared dispositive powerfinancial
"Shared Dispositive Power 21,626,763.00"
Investment Company Act of 1940regulatory
"investment company registered under the Investment Company Act of 1940"
A U.S. federal law that sets the rulebook for pooled investment vehicles such as mutual funds, exchange-traded funds and similar money managers, requiring them to register with regulators, disclose holdings and fees, limit conflicts of interest, and follow governance standards. It matters to investors because these protections and transparency rules act like a referee and scoreboard, helping people compare funds, trust that managers follow fair practices, and spot hidden costs or risks.
percent of classfinancial
"Percent of class: 5.3 %"
Percent of class is the portion of a specific category of securities—such as a company’s common shares, preferred shares, or a bond series—that takes part in or approves a corporate action (vote, consent, tender, etc.). Investors watch this number because it reveals how much support or opposition exists within that particular shareholder group; like counting how many members of a club back a proposal, it can determine whether a plan passes or how influence is distributed.
FAQ
AI-generated questions and answers. How Rhea-AI works. Not financial advice.
How many CoStar Group (CSGP) shares are beneficially owned by the Baron entities and Ronald Baron?
They report beneficial ownership of 21,626,763 CoStar Group common shares. This stake represents a significant holding and is disclosed as a group position across Baron Capital Group, BAMCO, Baron Capital Management, and Ronald Baron.
What percentage of CoStar Group (CSGP) does the Baron group own?
The Baron group reports owning 5.3% of CoStar Group’s outstanding common stock. This crosses the 5% threshold that requires disclosure and reflects a sizable institutional stake in the company.
How much voting power do the Baron entities have in CoStar Group (CSGP)?
They report 0 shares with sole voting power and 21,369,752 shares with shared voting power. Voting authority is therefore entirely shared among the Baron entities rather than held individually.
Who ultimately controls the Baron entities holding CoStar Group (CSGP) shares?
BAMCO and Baron Capital Management are subsidiaries of Baron Capital Group, Inc., and Ronald Baron owns a controlling interest in Baron Capital Group. Ronald Baron is also a U.S. citizen and a reporting person.
Do BAMCO and Baron Capital Management’s clients directly benefit from CoStar Group (CSGP) shares?
Yes. Advisory clients of BAMCO and Baron Capital Management have the right to receive dividends and sale proceeds from CoStar shares in their accounts, though no client is known to hold over 5% of the class.
Does any single client of the Baron entities own more than 5% of CoStar Group (CSGP)?
To the filers’ knowledge, no client has an interest in more than 5% of CoStar’s outstanding common stock. The 5.3% stake is spread across multiple advisory accounts.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
CoStar Group, Inc.
(Name of Issuer)
Common Stock ($0.01 par value)
(Title of Class of Securities)
22160N109
(CUSIP Number)
06/30/2026
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
Rule 13d-1(b)
Rule 13d-1(c)
Rule 13d-1(d)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
22160N109
1
Names of Reporting Persons
BAMCO INC /NY/
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
NEW YORK
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
18,463,177.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
18,720,188.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
18,720,188.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
4.58 %
12
Type of Reporting Person (See Instructions)
IA, CO
SCHEDULE 13G
CUSIP Number(s):
22160N109
1
Names of Reporting Persons
Baron Capital Group, Inc.
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
NEW YORK
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
21,369,752.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
21,626,763.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
21,626,763.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.3 %
12
Type of Reporting Person (See Instructions)
CO, HC
SCHEDULE 13G
CUSIP Number(s):
22160N109
1
Names of Reporting Persons
Baron Capital Management, Inc.
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
NEW YORK
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
2,906,575.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,906,575.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,906,575.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
0.71 %
12
Type of Reporting Person (See Instructions)
IA, CO
SCHEDULE 13G
CUSIP Number(s):
22160N109
1
Names of Reporting Persons
Ronald Baron
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
UNITED STATES
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
21,369,752.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
21,626,763.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
21,626,763.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.3 %
12
Type of Reporting Person (See Instructions)
HC, IN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
CoStar Group, Inc.
(b)
Address of issuer's principal executive offices:
1201 WILSON BLVD., ARLINGTON, VA, 22209
Item 2.
(a)
Name of person filing:
Baron Capital Group, Inc. ("BCG"),
BAMCO, Inc. ("BAMCO"),
Baron Capital Management, Inc. ("BCM"),
Ronald Baron
(b)
Address or principal business office or, if none, residence:
767 Fifth Avenue, 49th Floor,
New York, NY 10153
(c)
Citizenship:
BCG, BAMCO and BCM are New York corporations. Ronald Baron is a citizen of the United States.
(d)
Title of class of securities:
Common Stock ($0.01 par value)
(e)
CUSIP Number(s):
22160N109
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.
Ownership
(a)
Amount beneficially owned:
21,626,763
(b)
Percent of class:
5.3 %
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
0
(ii) Shared power to vote or to direct the vote:
21,369,752
(iii) Sole power to dispose or to direct the disposition of:
0
(iv) Shared power to dispose or to direct the disposition of:
21,626,763
Item 5.
Ownership of 5 Percent or Less of a Class.
Not Applicable
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
The advisory clients of BAMCO and BCM have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Issuer's common stock in their accounts. To the best of the Filing Persons' knowledge, no such person has such interest relating to more than 5% of the outstanding class of securities.
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary.
BAMCO and BCM are subsidiaries of BCG. Ronald Baron owns a controlling interest in BCG.
Item 8.
Identification and Classification of Members of the Group.
If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(K), so indicate under Item 3(k) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group.
See Item 3.
Item 9.
Notice of Dissolution of Group.
Not Applicable
Item 10.
Certifications:
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.
SIGNATURE
After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
