After four seasons as a junior player with four different teams, Bill Stewart was selected by the Sabres in the 1977 Amateur Draft and made his NHL debut in the 1977-78 season. He spent the majority of the season with the team's AHL affiliate in Hershey, but saw his first action in the Stanley Cup playoffs.
Stewart played the next season in Buffalo, only to be sent back to the minors for the next season. He started the year after in the minors until he was traded to the Blues, where he played the rest of the year, with the exception of two games with their CHL team in Salt Lake City. After two more seasons with the Blues organization, the majority of it in the minors, Stewart signed with the Leafs as a free agent in 1983.
After only two seasons in Toronto, Stewart was on the move once again, in 1985, when he signed as a free agent with the Minnesota North Stars. His stay in Minnesota lasted only eight games, while spending the majority of the 1985-86 season with the team's AHL affiliate in Springfield. This was Stewart's last NHL season. He went on to play in Italy for nine seasons before retiring from the game in 1995.