Mark Massey of AltaRock Partners Increases Amazon Stake, Sells Microsoft Shares in Q1 2026

AltaRock Partners' Mark Massey demonstrated a clear investment thesis in the first quarter of 2026, significantly increasing his stake in Amazon.com Inc. (AMZN) while reducing positions in several other major holdings and exiting several stocks entirely.

The most notable purchase during this period was the substantial increase in Amazon.com Inc (AMZN). Massey added over 2.5 million shares, representing a 3.46% increase in shares held compared to the previous quarter. This action pushed Amazon's portfolio allocation up to 38.2%, making it the largest position in his portfolio. Investors can learn more about Massey's investment approach by visiting his profile at https://www.insiderset.com/investor/mark-massey-altarock-partners.

Conversely, Massey significantly reduced his position in Microsoft Corp (MSFT). He sold over 214,000 shares, resulting in a 10.32% decrease in shares held and a corresponding reduction in MSFT's portfolio allocation to 16.75%. This was one of the largest sales during the quarter. For detailed information on Microsoft, please see https://www.insiderset.com/investors/stocks/MSFT.

Elsewhere, Massey maintained a strategic approach. He sold shares in TransDigm Group Inc (TDG), reducing the holdings by approximately 60,000 shares (-6.21% in shares) and lowering its portfolio allocation to 25.54%. Similarly, he sold Mastercard Inc-CLASS A (MA) and Visa Inc-CLASS A SHRS (V), both Financial Services stocks, though the reductions were smaller in percentage terms. Mastercard's allocation decreased slightly to 6.33%, and Visa's was reduced to 3.65%.

Mark Massey also completely exited several positions during the quarter. He sold all remaining shares in Moody's Corp (MCO), effectively removing it from his portfolio. Additionally, he sold all shares in Hilton Worldwide (HLT), which had been a very small holding (0.11% of the portfolio). Detailed profiles for Moody's and Hilton Worldwide are available at https://www.insiderset.com/investors/stocks/MCO and https://www.insiderset.com/investors/stocks/HLT, respectively.

Notably, Massey also sold a significant portion of his Alphabet Inc-CL A (GOOGL) holding, reducing the position by over 74% in terms of shares sold (-74.38% change) and lowering its allocation to just 0.3%. This was one of the more pronounced sales in the quarter.

In summary, Q1 2026 saw Mark Massey at AltaRock Partners focus on strengthening his position in Amazon while strategically reducing exposure in other tech and financial services companies, ultimately exiting several smaller holdings entirely.