Breaking down the stocks Mark Massey and Scott Bradford (AltaRock Partners) bought, sold, and held in Q3 2025, including their holdings at the end of the quarter. All data sourced from AltaRock Partners' 13F filed on November 14, 2025.
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
Q3 '25 13F filed with SEC
Holdings in Q3 2025
| Ticker | Company | Weight | Change | Value |
|---|---|---|---|---|
| AMZN | Amazon | 30.3% | Added (+20%) | $1.66B |
| MSFT | Microsoft | 24.3% | Trimmed (-0%) | $1.33B |
| TDG | TransDigm | 23.5% | Trimmed (-0%) | $1.29B |
| MCO | Moody's | 8.3% | Trimmed (-0%) | $452.05M |
| MA | Mastercard | 6.1% | Trimmed (-0%) | $332.23M |
| V | Visa | 3.3% | Trimmed (-0%) | $182.13M |
| HLT | Hilton | 2.6% | Trimmed (-0%) | $140.78M |
| GOOGL | Alphabet | 1.5% | Trimmed (-67%) | $83.72M |
| FICO | Fair Isaac | 0.0% | Trimmed (-0%) | $998.19K |
Current Investment Strategy
AltaRock Partners maintained its ultra-concentrated value investing approach in Q3 2025, deploying $5.5 billion across just nine stocks with Amazon, Microsoft, and TransDigm Group representing nearly 80% of the portfolio. The firm, led by Harvard MBAs Mark Massey and Scott Bradford, significantly bolstered its largest position by adding 20% to its Amazon stake while trimming holdings in aerospace manufacturer TransDigm, Microsoft, credit rating agency Moody's, and payments processor Mastercard, reflecting their disciplined focus on businesses with durable competitive moats and strong free cash flow generation.
New Investments
AltaRock Partners did not open any new positions during Q3 2025.
Added, Trimmed, and Exited
Added
AltaRock Partners increased its position in Amazon (AMZN), adding approximately 1.28 million shares to bring the total holding to 7.56 million shares valued at $1.66 billion.
What it means: This significant 20% increase in share count demonstrates strong conviction in Amazon's business trajectory. The addition came during a quarter when Amazon delivered strong returns (+20.5%), suggesting the firm is doubling down on a winner. For an ultra-concentrated investor like AltaRock that typically holds fewer than ten positions, this move signals Amazon has likely become their largest or second-largest position, reinforcing their belief in the company's durable competitive advantages in e-commerce and cloud computing.
Trimmed
AltaRock Partners made one substantial reduction, cutting Alphabet (GOOGL) by approximately 701,000 shares (a 67% reduction in position size), while making minimal trims across Microsoft (MSFT), TransDigm (TDG), Moody's (MCO), Mastercard (MA), Hilton (HLT), Visa (V), and Fair Isaac (FICO)—each reduced by less than 0.5%.
What it means: The dramatic reduction in Alphabet, which experienced a -54.6% return during the quarter, represents a significant loss of confidence in the position. This is particularly noteworthy for a long-term, concentrated investor like AltaRock that typically holds positions through volatility. The severity of the trim suggests concerns beyond temporary market fluctuations—potentially related to competitive pressures in AI, regulatory challenges, or fundamental business deterioration. The minor trims across other holdings appear to be routine portfolio rebalancing, with the proceeds likely redirected to Amazon. This marks a clear shift in AltaRock's conviction between the two mega-cap tech giants.
Exited
AltaRock Partners did not completely exit any positions during the 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.
