3 institutions reported holding $38.3M of WATSCO INC (WSO.B) in SEC 13F filings for 2026-03-31. Largest institutional holders: GROUP ONE TRADING LLC ($25.5M), IMC-Chicago, LLC ($12.7M), SIMPLEX TRADING, LLC ($181,895). Source: SEC Form 13F.
| Rank | Institution | Value | Shares | Change |
|---|---|---|---|---|
| 1 | GROUP ONE TRADING LLC | $25.5M | 70,000 | Added |
| 2 | IMC-Chicago, LLC | $12.7M | 34,900 | New |
| 3 | SIMPLEX TRADING, LLC | $181,895 | 500 | Trimmed |
Source: SEC Form 13F filings · as of 2026-03-31