Born in Port Colborne, Ontario, on Nov. 4, 1935, Gregory grew up in nearby Dunnville and moved to Toronto to attend St. Michael's College School in 1953. He won the Memorial Cup as general manager of St. Michael's Majors in 1961 and as coach of the Toronto Marlboros in 1964, then assumed a managerial role with the Marlboros and guided them to the Memorial Cup again in 1967.
The Maple Leafs hired Gregory to coach Vancouver, their minor league affiliate, in 1967-68. He joined them as a scout in 1968 and a year later, at age 33, was promoted to general manager.