QMCO Institutional Ownership & Shareholders
QUANTUM CORP (QMCO) is currently held by 69 institutional investors tracked by InsiderSet, with a combined reported market value of approximately $166.62M based on the latest available SEC Form 13F filings for the quarter ended June 30, 2026.
Two Seas Capital Lp is currently the largest disclosed institutional shareholder of QMCO tracked by InsiderSet, reporting ownership valued at approximately $47.29M in its September 30, 2026 SEC Form 13F filing. Based on current market prices and the latest disclosed share count, the position is now estimated to be worth approximately $24.94M, representing an estimated loss of -47.26% since the filing period.
The top 10 institutional shareholders tracked on this page collectively account for approximately 86% of the total disclosed QMCO value among the investors covered in this analysis. Major shareholders include Two Seas Capital Lp, Alyeska Investment Group, L.P., Oaktree Capital Management, and several other long-term asset managers with concentrated positions in QUANTUM CORP (QMCO).
This page ranks the largest institutional QMCO shareholders using publicly disclosed SEC Form 13F data, including reported values, estimated current holding values, portfolio allocation percentages, ownership concentration metrics, and historical holding changes across major hedge funds and investment firms.
Institutional Holders
69
Total Reported Value
$166.62M
Largest Holder
Two Seas Capital Lp
Largest Position
$47.29M
Insider Transactions (90d)
7
Latest Filing Quarter
Q2 2026
New Institutional Positions
84
Funds Exiting Positions
0
| Name | Investor/Manager | Portfolio % | Quantity | Reported Balance | Current Estimated Value | Gain/loss Since Filing | Estimated Portfolio Performance |
|---|---|---|---|---|---|---|---|
| Two Seas Capital Lp | 1.88% | 1,490,992 | $47,294,266 | $24,944,296 | -$22,349,970 | -47.26% | |
| Alyeska Investment Group, L.P. | 0.08% | 2,653,928 | $29,193,208 | $44,400,215 | +$15,207,007 | +52.09% | |
| Oaktree Capital Management | Howard Marks | 0.42% | 2,011,678 | $22,128,458 | $33,655,373 | +$11,526,915 | +52.09% |
| Portolan Capital Management, Llc | 0.42% | 1,020,120 | $11,221,320 | $17,066,608 | +$5,845,288 | +52.09% | |
| Ashford Capital Management Inc | 1.13% | 1,039,200 | $10,551,200 | $17,385,816 | +$6,834,616 | +64.78% | |
| Marshall Wace, Llp | 0.01% | 713,075 | $7,843,825 | $11,929,745 | +$4,085,920 | +52.09% | |
| Vanguard Capital Management Llc | 0.00% | 605,541 | $6,660,951 | $10,130,701 | +$3,469,750 | +52.09% | |
| Manatuck Hill Partners, Llc | 1.28% | 350,000 | $3,850,000 | $5,855,500 | +$2,005,500 | +52.09% | |
| Blackrock, Inc. | 0.00% | 273,030 | $3,003,330 | $4,567,792 | +$1,564,462 | +52.09% | |
| Cinctive Capital Management Lp | 0.08% | 182,769 | $2,010,459 | $3,057,725 | +$1,047,266 | +52.09% | |
| Bank Of America Corp | 0.00% | 170,130 | $1,871,430 | $2,846,275 | +$974,845 | +52.09% | |
| Geode Capital Management, Llc | 0.00% | 164,600 | $1,811,524 | $2,753,758 | +$942,234 | +52.01% | |
| Renaissance Technologies LLC | Jim Simons | 0.00% | 154,516 | $1,699,676 | $2,585,053 | +$885,377 | +52.09% |
| Sona Asset Management (Us) Llc | 0.06% | 150,000 | $1,650,000 | $2,509,500 | +$859,500 | +52.09% | |
| Walleye Capital Llc | 0.01% | 120,044 | $1,320,484 | $2,008,336 | +$687,852 | +52.09% | |
| Raymond James Financial Inc | 0.00% | 103,836 | $1,142,196 | $1,737,176 | +$594,980 | +52.09% | |
| Centiva Capital, Lp | 0.04% | 100,000 | $1,100,000 | $1,673,000 | +$573,000 | +52.09% | |
| Vanguard Fiduciary Trust Co | 0.00% | 89,125 | $980,375 | $1,491,061 | +$510,686 | +52.09% | |
| Kkm Financial Llc | 0.13% | 90,274 | $960,515 | $1,510,284 | +$549,769 | +57.24% | |
| Qube Research & Technologies Ltd | 0.00% | 80,977 | $890,747 | $1,354,745 | +$463,998 | +52.09% | |
| State Street Corp | 0.00% | 75,914 | $835,054 | $1,270,041 | +$434,987 | +52.09% | |
| Cygnus Capital Advisors, Llc | 0.56% | 74,323 | $818,000 | $1,243,424 | +$425,424 | +52.01% | |
| Susquehanna International Group, Llp | 0.00% | 69,775 | $767,525 | $1,167,336 | +$399,811 | +52.09% | |
| Man Group Plc | 0.00% | 68,593 | $754,523 | $1,147,561 | +$393,038 | +52.09% | |
| Informed Momentum Co Llc | 0.06% | 64,857 | $713,427 | $1,085,058 | +$371,631 | +52.09% | |
| Y-Intercept (Hong Kong) Ltd | 0.02% | 21,886 | $694,224 | $366,153 | -$328,071 | -47.26% | |
| Ubs Group Ag | 0.00% | 46,106 | $507,166 | $771,353 | +$264,187 | +52.09% | |
| Sei Investments Co | 0.00% | 38,739 | $426,150 | $648,103 | +$221,953 | +52.08% | |
| Susquehanna Fundamental Investments, Llc | 0.01% | 34,601 | $380,611 | $578,875 | +$198,264 | +52.09% | |
| Squarepoint Ops Llc | 0.00% | 33,817 | $371,987 | $565,758 | +$193,771 | +52.09% | |
| Northern Trust Corp | 0.00% | 33,220 | $365,420 | $555,771 | +$190,351 | +52.09% | |
| Flagship Harbor Advisors, Llc | 0.01% | 11,004 | $349,047 | $184,097 | -$164,950 | -47.26% | |
| Price T Rowe Associates Inc | 0.00% | 25,069 | $276,000 | $419,404 | +$143,404 | +51.96% | |
| Millennium Management Llc | 0.00% | 21,755 | $239,305 | $363,961 | +$124,656 | +52.09% | |
| Calamos Advisors Llc | 0.00% | 6,770 | $214,744 | $113,262 | -$101,482 | -47.26% | |
| True Private Wealth Advisors | 0.02% | 6,645 | $210,779 | $111,171 | -$99,608 | -47.26% | |
| Goldman Sachs Group Inc | 0.00% | 19,153 | $210,683 | $320,430 | +$109,747 | +52.09% | |
| Bridgeway Capital Management, Llc | 0.00% | 16,240 | $178,640 | $271,695 | +$93,055 | +52.09% | |
| Morgan Stanley | 0.00% | 15,492 | $170,412 | $259,181 | +$88,769 | +52.09% | |
| Citigroup Inc | 0.00% | 14,426 | $158,686 | $241,347 | +$82,661 | +52.09% | |
| Kovack Advisors, Inc. | 0.01% | 13,430 | $146,790 | $224,684 | +$77,894 | +53.06% | |
| Schonfeld Strategic Advisors Llc | 0.00% | 12,055 | $132,605 | $201,680 | +$69,075 | +52.09% | |
| Wells Fargo & Company/Mn | 0.00% | 11,300 | $124,300 | $189,049 | +$64,749 | +52.09% | |
| Invesco Ltd. | 0.00% | 10,839 | $119,229 | $181,336 | +$62,107 | +52.09% | |
| Vanguard Global Advisers, Llc | 0.00% | 6,000 | $66,000 | $100,380 | +$34,380 | +52.09% | |
| Jpmorgan Chase & Co | 0.00% | 3,680 | $43,608 | $61,566 | +$17,958 | +41.18% | |
| Sbi Securities Co., Ltd. | 0.00% | 1,324 | $41,997 | $22,151 | -$19,846 | -47.26% | |
| Signaturefd, Llc | 0.00% | 696 | $22,077 | $11,644 | -$10,433 | -47.26% | |
| Jones Financial Companies Lllp | 0.00% | 1,580 | $18,407 | $26,433 | +$8,026 | +43.61% | |
| Carolina Wealth Advisors, Llc | 0.01% | 416 | $13,196 | $6,960 | -$6,236 | -47.26% |
Frequently asked questions about QMCO
Who are the largest institutional holders of QMCO?
The largest institutional holders of QMCO reported in the latest SEC Form 13F filings include Two Seas Capital Lp, Alyeska Investment Group, L.P., Oaktree Capital Management, Portolan Capital Management, Llc, and Ashford Capital Management Inc. InsiderSet ranks institutional holders by their latest reported QMCO position.
What is QMCO institutional ownership?
This page tracks QMCO positions reported by institutional investment managers through SEC Form 13F. QUANTUM CORP (QMCO) institutional ownership on InsiderSet reflects disclosed 13F holdings among the managers we analyze, not every shareholder of the stock.
How many institutions own QMCO?
InsiderSet currently tracks 69 institutional managers reporting QMCO holdings in the latest available 13F data. This count reflects institutions included in the SEC Form 13F filings analyzed by InsiderSet and should not be interpreted as the total number of QMCO shareholders.
How much QMCO stock do institutions own?
Institutional investment managers disclosed approximately $166.62M in QMCO holdings for Q2 2026. This figure is reported 13F value as of the filing period, not necessarily today's market value.
When was QMCO institutional ownership last updated?
The latest QMCO institutional ownership data on InsiderSet is based on SEC Form 13F filings for the quarter ended June 30, 2026. Form 13F filings are generally reported after the quarter ends, so the holdings shown represent the latest publicly disclosed positions rather than real-time institutional holdings.
Are institutional QMCO holdings real-time?
No. Form 13F data is not real-time. It represents positions reported by institutional investment managers as of the end of the reporting quarter. An institution may have changed its QMCO position after the reporting date.
Are institutions buying or selling QMCO?
Institutional buying and selling can be analyzed by comparing QMCO positions across consecutive 13F reporting periods. InsiderSet's QMCO Ownership Changes page shows institutions that increased, reduced, initiated, or exited positions based on reported 13F holdings. View QMCO ownership changes.
How has QMCO institutional ownership changed over time?
InsiderSet tracks QMCO institutional holdings across multiple 13F reporting periods, allowing investors to compare institutional holder counts, reported value, and reported shares over time.