Born in Carbonear, Newfoundland, he was educated at St. Andrew's College (Aurora, Ontario). Moores then briefly attended Boston University, but left after two months to return to Newfoundland, where he worked in a fish plant. His father was a wealthy businessman in that industry (The Insiders, by John Sawatsky, 1987).
Moores was first elected in 1968 to the House of Commons as a Progressive Conservative. In 1970, he became leader of the Progressive Conservative Party of Newfoundland, and was asked to form a government in January 1972, several months following the October 1971 election that resulted in a near tie between Joey Smallwood's Liberals and the Tories.
As Premier, Moores advocated rural development and provincial control of natural resources as well as economic development.
He left politics in 1979 to re-enter business and became a lobbyist. In 1983, he was an organizer of the successful Progressive Conservative Party leadership campaign for Brian Mulroney (Brian Mulroney: The Politics of Ambition, by John Sawatsky, 1991). He served as an adviser to Mulroney while he was Prime Minister of Canada, and was appointed to the Board of Air Canada, then a Crown Corporation. At the time, he was also working for Government Consultants International (GCI), a powerful Ottawa-based international lobbying firm, which had as clients at the time the airline firms Wardair and Nordair, which were competitors of Air Canada. Over accusations of conflict of interest, GCI then gave up Wardair and Nordair as clients. He resigned his Air Canada directorship shortly after GCI took on the Airbus file (The Insiders, by John Sawatsky, 1987; On The Take, by Stevie Cameron, 1994).
In 1987, he became the chairman of GCI. In the 1990s, he regained prominence through his alleged role in the Airbus affair.
Moores died of cancer in Perth, Ontario.
In November 2007, in the wake of new revelations about the Airbus affair by Karlheinz Schreiber, The Globe and Mail published evidence indicating that Moores had written a letter about the Airbus deal to Franz Josef Strauss, chairman of Airbus Industrie. Until his death Moores denied having any involvement in the affair.