ATS CORP (ATS) Top Institutional Shareholders
ATS CORP (ATS) is currently reported in institutional portfolios tracked by InsiderSet based on the latest available SEC Form 13F filings for the quarter ended March 31, 2026. The institutional investors covered on this page collectively reported approximately $2.37B in ATS holdings during the latest filing period.
Mason Capital Management Llc is currently the largest disclosed institutional shareholder of ATS tracked by InsiderSet, reporting ownership valued at approximately $462.60M in its March 31, 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 $464.57M, representing an estimated gain of +0.43% since the filing period.
The top 10 institutional shareholders tracked on this page collectively account for approximately 67% of the total disclosed ATS value among the investors covered in this analysis. Major shareholders include Mason Capital Management Llc, Turtle Creek Asset Management, Royal Bank Of Canada, and several other long-term asset managers with concentrated positions in ATS CORP (ATS).
This page ranks the largest institutional ATS 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
126
Total Reported Value
$2.37B
Largest Holder
Mason Capital Management Llc
Largest Position
$462.60M
Insider Transactions (90d)
0
Latest Filing Quarter
Q1 2026
New Institutional Positions
142
Funds Exiting Positions
0
| Name | Investor/Manager | Portfolio % | Quantity | Reported Balance | Current Estimated Value | Gain/loss Since Filing | Estimated Portfolio Performance |
|---|---|---|---|---|---|---|---|
| Mason Capital Management Llc | 75.48% | 16,404,170 | $462,597,594 | $464,566,094 | +$1,968,500 | +0.43% | |
| Turtle Creek Asset Management | Andrew Brenton | 7.46% | 10,385,819 | $292,880,096 | $294,126,394 | +$1,246,298 | +0.43% |
| Royal Bank Of Canada | 0.04% | 7,761,838 | $218,884,000 | $219,815,252 | +$931,252 | +0.43% | |
| Edgepoint Investment Group Inc. | 1.62% | 7,168,112 | $202,081,247 | $203,000,932 | +$919,685 | +0.46% | |
| Bank Of Montreal | 0.04% | 3,115,360 | $87,827,288 | $88,226,995 | +$399,707 | +0.46% | |
| Fairfax Financial Holdings | Prem Watsa | 3.57% | 2,486,400 | $69,352,987 | $70,414,848 | +$1,061,861 | +1.53% |
| Vanguard Capital Management Llc | 0.00% | 2,366,730 | $66,708,652 | $67,025,794 | +$317,142 | +0.48% | |
| Janus Henderson Group Plc | 0.03% | 2,297,214 | $64,543,983 | $65,057,100 | +$513,117 | +0.79% | |
| Fmr Llc | 0.00% | 2,277,472 | $64,193,571 | $64,498,007 | +$304,436 | +0.47% | |
| Connor, Clark & Lunn Investment Management Ltd. | 0.15% | 2,264,757 | $63,847,345 | $64,137,918 | +$290,573 | +0.46% | |
| Ack Asset Management Llc | 6.50% | 1,846,196 | $52,062,727 | $52,284,271 | +$221,544 | +0.43% | |
| Fil Ltd | 0.04% | 1,778,181 | $50,088,280 | $50,358,086 | +$269,806 | +0.54% | |
| Td Waterhouse Canada Inc. | 0.14% | 1,634,449 | $46,872,536 | $46,287,596 | -$584,940 | -1.25% | |
| Hill City Capital, Lp | 1.66% | 1,649,857 | $46,525,967 | $46,723,950 | +$197,983 | +0.43% | |
| Td Asset Management Inc | 0.03% | 1,422,459 | $39,966,047 | $40,284,039 | +$317,992 | +0.80% | |
| Vinva Investment Management Ltd | 0.45% | 2,088,947 | $36,514,794 | $59,158,979 | +$22,644,185 | +62.01% | |
| Van Lanschot Kempen Investment Management N.V. | 0.30% | 863,486 | $33,857,286 | $24,453,924 | -$9,403,362 | -27.77% | |
| Scheer, Rowlett & Associates Investment Management Ltd. | 2.40% | 1,181,937 | $33,320,811 | $33,472,456 | +$151,645 | +0.46% | |
| Clearbridge Investments, Llc | 0.03% | 1,091,291 | $30,774,410 | $30,905,361 | +$130,951 | +0.43% | |
| Marathon Asset Management Ltd | 1.18% | 1,093,911 | $30,733,509 | $30,979,560 | +$246,051 | +0.80% | |
| Bank Of America Corp | 0.00% | 945,875 | $26,673,675 | $26,787,180 | +$113,505 | +0.43% | |
| Alberta Investment Management Corp | 0.16% | 940,191 | $26,505,581 | $26,626,209 | +$120,628 | +0.46% | |
| Mirae Asset Global Etfs Holdings Ltd. | 0.03% | 758,313 | $21,305,903 | $21,475,424 | +$169,521 | +0.80% | |
| Massachusetts Financial Services Co | 0.01% | 533,957 | $20,936,454 | $15,121,662 | -$5,814,792 | -27.77% | |
| Vanguard Fiduciary Trust Co | 0.01% | 728,058 | $20,521,043 | $20,618,603 | +$97,560 | +0.48% | |
| National Bank Of Canada | 0.02% | 648,282 | $18,112,231 | $18,359,346 | +$247,115 | +1.36% | |
| Principal Financial Group Inc | 0.01% | 620,840 | $17,443,399 | $17,582,189 | +$138,790 | +0.80% | |
| Mackenzie Financial Corp | 0.02% | 616,504 | $17,374,486 | $17,459,393 | +$84,907 | +0.49% | |
| Legal & General Group Plc | 0.00% | 611,689 | $17,239,326 | $17,323,032 | +$83,706 | +0.49% | |
| 1832 Asset Management L.P. | 0.01% | 401,696 | $11,327,827 | $11,376,031 | +$48,204 | +0.43% | |
| Public Sector Pension Investment Board | 0.03% | 356,837 | $10,059,841 | $10,105,624 | +$45,783 | +0.46% | |
| Cibc World Market Inc. | 0.02% | 346,606 | $9,767,357 | $9,815,882 | +$48,525 | +0.50% | |
| Invesco Ltd. | 0.00% | 343,176 | $9,677,563 | $9,718,744 | +$41,181 | +0.43% | |
| Vanguard Global Advisers, Llc | 0.00% | 258,998 | $7,300,118 | $7,334,823 | +$34,705 | +0.48% | |
| Franklin Resources Inc | 0.00% | 247,467 | $6,976,515 | $7,008,265 | +$31,750 | +0.46% | |
| Charles Schwab Investment Management Inc | 0.00% | 238,654 | $6,705,330 | $6,758,681 | +$53,351 | +0.80% | |
| Ubs Group Ag | 0.00% | 227,628 | $6,419,110 | $6,446,425 | +$27,315 | +0.43% | |
| Waratah Capital Advisors Ltd. | 0.57% | 223,983 | $6,316,321 | $6,343,199 | +$26,878 | +0.43% | |
| Dixon Mitchell Investment Counsel Inc. | 0.21% | 211,025 | $5,929,053 | $5,976,228 | +$47,175 | +0.80% | |
| Scotia Capital Inc. | 0.02% | 192,530 | $5,379,680 | $5,452,450 | +$72,770 | +1.35% | |
| Focus Partners Wealth | 0.01% | 181,975 | $5,131,695 | $5,153,532 | +$21,837 | +0.43% | |
| Royce & Associates Lp | 0.05% | 179,500 | $5,059,446 | $5,083,440 | +$23,994 | +0.47% | |
| Arrowmark Colorado Holdings Llc | 0.13% | 174,000 | $4,906,800 | $4,927,680 | +$20,880 | +0.43% | |
| Granite Investment Partners, Llc | 0.30% | 173,031 | $4,879,474 | $4,900,238 | +$20,764 | +0.43% | |
| Montrusco Bolton Investments Inc. | 0.07% | 170,956 | $4,803,257 | $4,841,474 | +$38,217 | +0.80% | |
| Sei Investments Co | 0.00% | 167,820 | $4,732,524 | $4,752,662 | +$20,138 | +0.43% | |
| Swiss National Bank | 0.00% | 164,400 | $4,627,014 | $4,655,808 | +$28,794 | +0.62% | |
| First Trust Advisors Lp | 0.00% | 154,403 | $4,352,053 | $4,372,693 | +$20,640 | +0.47% | |
| Candelo Capital Management Lp | 4.30% | 151,688 | $4,274,759 | $4,295,804 | +$21,045 | +0.49% | |
| Cibc Asset Management Inc | 0.01% | 134,186 | $3,770,291 | $3,800,148 | +$29,857 | +0.79% |
Frequently asked questions about ATS
Who owns the most ATS stock?
The largest holders of ATS are typically major institutional investors such as asset managers and hedge funds reporting on Form 13F. The table above ranks tracked superinvestors by reported position size using the latest available filings for ATS CORP (ATS).
Is ATS widely held by superinvestors?
Many widely followed stocks like ATS appear across numerous superinvestor portfolios because of liquidity, index inclusion, and fundamentals. The holder count and table above show how broadly ATS is represented among the institutional managers we track.
What do “Current Estimated Value”, “Gain/loss Since Filing”, and “Estimated Portfolio Performance” mean?
Current Estimated Value is reported share quantity from the latest 13F times our most recent split-adjusted U.S. session close. Gain/loss Since Filing is that estimate minus the reported 13F dollar value; Estimated Portfolio Performance is that difference as a percent of the reported value. Green means the estimate is above the filing value; red means below (not purchase cost). If many filers share the same implied filing price per share, the performance % may match across rows. These are not official fund marks or live quotes.