Breaking down the stocks Mark Massey and Scott Bradford (AltaRock Partners) bought, sold, and held in Q1 2026, including their holdings at the end of the quarter. All data sourced from AltaRock Partners' 13F filed on May 15, 2026.
Who are Mark Massey, Scott Bradford and AltaRock Partners?
AltaRock Partners is a highly concentrated investment firm founded by Mark Massey and Scott Bradford, both Harvard MBA graduates with distinguished investment backgrounds. Massey previously worked at Seth Klarman's Baupost Group, while Bradford gained experience at Fiduciary Management Associates. The firm maintains an extremely focused portfolio typically comprising fewer than ten holdings with a combined value of approximately $4.8 billion. AltaRock's investment philosophy centers on identifying exceptional businesses with durable competitive advantages and holding them for the long term.
Altarockpartners.com
Q1 '26 13F filed with SEC
Holdings in Q1 2026
| Ticker | Company | Weight | Change | Value |
|---|---|---|---|---|
| AMZN | Amazon | 38.2% | Added (+3%) | $1576.18B |
| TDG | TransDigm | 25.5% | Trimmed (-6%) | $1053.69B |
| MSFT | Microsoft | 16.8% | Trimmed (-10%) | $691.31B |
| MCO | Moody's | 9.1% | Added (+6%) | $376.06B |
| MA | Mastercard | 6.3% | Trimmed (-4%) | $261.24B |
| V | Visa | 3.7% | Trimmed (-3%) | $150.72B |
| GOOGL | Alphabet | 0.3% | Trimmed (-74%) | $12.48B |
| HLT | Hilton | 0.1% | Trimmed (-97%) | $4.66B |
Current Investment Strategy
Inspired by the Buffett-Munger tradition of owning exceptional businesses, Mark Massey and Scott Bradford's AltaRock Partners ran an ultra-concentrated, low-turnover portfolio of eight wide-moat compounders as of the end of Q1 2026, anchored by dominant stakes in Amazon, TransDigm Group, and Microsoft — with the top three positions accounting for the bulk of a roughly $4.1 billion book — alongside durable franchises in payments (Mastercard, Visa), credit analytics (Moody's), aerospace and defense (TransDigm), and hospitality (Hilton). The Beverly, Massachusetts-based firm, which treats each holding as a subsidiary in what it calls "The AltaRock Conglomerate," initiated no new positions and made no full exits in the quarter, reflecting its hallmark patience and deep conviction in businesses it believes will generate materially higher earnings over the next decade or more.
New Investments
AltaRock Partners did not open any new positions during Q1 2026.
Added, Trimmed, and Exited
Added
AltaRock Partners added to two existing positions in Q1 2026: Amazon (AMZN) received the larger addition with 253,412 new shares (+3.5%), bringing the total to 7,567,946 shares, while Moody's (MCO) saw a modest increase of 47,533 shares (+5.8%), bringing that holding to 862,036 shares.
What it means: The additions to Amazon (AMZN) and Moody's (MCO) suggest AltaRock is doubling down on high-quality compounders with durable moats — a cloud/e-commerce giant and a near-monopoly in credit ratings. Given that the firm trimmed several other names simultaneously, these adds appear deliberate and conviction-driven, likely reflecting the managers' view that both businesses remain attractively valued relative to their long-term earnings power.
Trimmed
AltaRock Partners trimmed six positions during the quarter: Hilton (HLT) was slashed dramatically by 527,272 shares (a ~97% reduction, from 542,613 to just 15,341 shares), Alphabet (GOOGL) was cut by 126,000 shares (~74%), Microsoft (MSFT) was reduced by 214,820 shares (~10%), TransDigm (TDG) was trimmed by 60,232 shares (~6%), and both Mastercard (MA) and Visa (V) saw modest reductions of 19,000 and 18,000 shares (~3.5%) respectively.
What it means: The near-complete exit from Hilton (HLT) and the heavy reduction in Alphabet (GOOGL) are the standout moves. Hilton's near-liquidation suggests the position may have reached AltaRock's estimate of fair value, or capital was being redeployed into higher-conviction names. The dramatic cut in Alphabet (GOOGL) could reflect growing concerns about competitive pressures in search from AI alternatives, or again, valuation discipline. The lighter trims across Microsoft (MSFT), TransDigm (TDG), Mastercard (MA), and Visa (V) look more like portfolio rebalancing — trimming winners or managing position sizing — rather than a fundamental change in thesis for those businesses.
Exited
AltaRock Partners did not fully exit any position this quarter.
Disclaimer: All posts are for informational purposes only. They are NOT a recommendation to buy or sell the securities discussed. Please do your own research and due diligence before investing your money.
