A very popular player with the nearby St. Catharines' Blackhawks OHL franchise, McAdam was drafted by the Buffalo Sabres 53rd overall in the 1975 Entry Draft. He would quickly form an effective unit with Terry Martin and Fred Stanfield.
In February 1979, McAdam was traded to the Pittsburgh Penguins for veteran enforcer Dave "The Hammer" Schultz. The trade proved good for McAdam, as he matched a career high with 19 goals well working on a line with Greg Malone and Paul Marshall.
McAdam quickly descended into the role of vagabond, bouncing around the league with the Detroit Red Wings, Calgary Flames, Washington Capitals, New Jersey Devils, Toronto Maple Leafs, and briefly the Buffalo Sabres for a second time. His great speed made him a popular player everywhere he played.
In his retirement, McAdam moved to Portland, Maine and went to work for United Parcel Service. However he would end up suing the Maine workman's compensation board in 2000, claiming it had to pay for his efforts to find a proper program for rehabilitation from an injury. The case went to the Maine Supreme Judicial Court, where the judges sided with McAdam and insisted that future injury evaluations be paid for and conducted by the board itself. As a result, McAdam attended Southern Maine Technical College and became a physical therapy assistant after receiving his associate's degree.