Mark Massey portfolio
Updated November 15, 2026
Mark Massey (AltaRock Partners) — A very concentrated portfolio of a few excellent companies held for years.
According to the latest 13F report that AltaRock Partners filed with the SEC (Q3 2026, filed November 13, 2026), its US stock portfolio is worth about $4.2B across 8 holdings. The largest positions are Microsoft CorpMSFT, Amazon.com IncAMZN, Transdigm Group IncTDG, and the top 10 make up 100% of the portfolio.
| # | Stock | Weight | Value | Change this quarter |
|---|---|---|---|---|
| 1 | Microsoft CorpMSFT | 32.1% | $1.4B | Added +13% |
| 2 | Amazon.com IncAMZN | 28.5% | $1.2B | Trimmed +16% |
| 3 | Transdigm Group IncTDG | 21.7% | $913M | Trimmed +4% |
| 4 | Mastercard Inc - AMA | 9.2% | $388M | Trimmed +8% |
| 5 | Visa Inc-class A SharesV | 6.6% | $277M | Trimmed +8% |
| 6 | Moody's CorpMCO | 1.4% | $60M | Trimmed +56% |
| 7 | Alphabet Inc-cl AGOOGL | 0.3% | $14M | Trimmed +5% |
| 8 | Hilton Worldwide Holdings INHLT | 0.1% | $5M | — |
Frequently asked questions
What does Mark Massey own now?
According to the latest 13F (Q3 2026), the largest holdings are Microsoft CorpMSFT, Amazon.com IncAMZN, Transdigm Group IncTDG. The full list is in the table above.
What is a 13F report?
US investment managers with more than $100 million in US stocks must list their holdings with the SEC within 45 days after each quarter ends.
Why is the data delayed?
Because 13F reports arrive up to 45 days after the quarter ends, the manager may have traded since then.
Should I copy this portfolio?
Knowing what great investors buy is a good source of ideas, but because of the delay and different goals, copying blindly is not recommended.
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