The chief executives of Inc., Facebook Inc., Alphabet Inc. and Apple Inc. will testify before a rescheduled congressional hearing on antitrust in big tech on July 29, according to an announcement from the House Judiciary Committee.

The hearing with Jeff Bezos, Mark Zuckerberg, Sundar Pichai and Tim Cook was originally scheduled for July 27 but was postponed because of plans to honor the late civil rights icon John Lewis at the Capitol.

“Given the central role these corporations play in the lives of the American people, it is critical that their CEOs are forthcoming,” Democratic Representatives Jerrold Nadler and David Cicilline, who respectively chair the judiciary panel and its antitrust subcommittee, said in a joint statement.

The hearing, where the executives will testify virtually, is the most high-profile showdown yet between tech executives and lawmakers, who are increasingly frustrated with the technology industry. The hearing will start at noon EDT.

The companies all face antitrust investigations by federal enforcers, as well as a yearlong probe by the House which is likely to end with recommended changes to competition law.

Facebook is also planning to announce quarterly earnings July 29.