Next Monday, a House antitrust subcommittee will grill a quartet of CEOs from Apple, Amazon, Google and Facebook, but the committee has already prepped for a related investigation into the sector by quizzing a top executive from another tech giant: Microsoft. 

Several weeks ago, the subcommittee interviewed Brad Smith, president and chief legal officer of Microsoft, via videoconference, according to people with knowledge of the meeting. While the committee invited Smith primarily so he could provide Microsoft’s perspective as a big tech company that has previously faced antitrust regulation, during the session the Microsoft executive also discussed his company’s concerns about the way Apple operates its App Store. That issue is at the heart of regulators’ scrutiny of Apple in the U.S. and Europe.