The report says that at the same time Mr. Barrack was seeking to become the administration’s Middle East envoy or ambassador to the United Arab Emirates, he was exploring the possibility that his private equity firm, Colony Capital, would be part of a deal to purchase Westinghouse Electric Company, the sole American manufacturer of large-scale nuclear reactors — partly with capital from Saudi Arabia or its close ally, the United Arab Emirates.

The idea was that Westinghouse would then be well positioned to bid for Saudi government business building nuclear power plants. Because the United States carefully regulates the transfer of nuclear technology to prevent the spread of nuclear weapons, any such deal would require the approval of Congress and the administration.

An early contender for that business was a private company called IP3 International, which had assembled a consortium of American companies eager to get in on what could have amounted to a multibillion dollar deal. Before he became Mr. Trump’s national security adviser — a post he held for less than a month — Mr. Flynn had listed himself as an adviser to IP3. Officials at IP3 said that the listing was in error and that Mr. Flynn was not associated with the company.

The Oversight Committee investigators tried to explore questions that federal prosecutors in the United States attorney’s office in Brooklyn have been scrutinizing for months: whether Mr. Barrack, who led financing efforts for Mr. Trump’s 2016 campaign and inauguration, tried to shape the Trump team’s message in favor of the governments of Saudi Arabi and the United Arab Emirates, where his firm has done hundreds of millions of dollars in business.

Mr. Barrack was in close touch during the campaign, transition and early administration with people well connected to the ruling family of the United Arab Emirates, including Mr. al-Malik and Yousef al-Otaiba, the powerful Emirati ambassador to the United States.

In May 2016, Mr. Barrack sent Mr. al-Malik a draft of an energy policy speech that Mr. Trump, then closing in on the Republican presidential nomination, was to deliver that month in North Dakota, asking for pro-gulf region language. According to the report, Mr. al-Malik, who has been interviewed by federal prosecutors, “circulated the draft among Emirati and Saudi officials.”