After a stellar final year of junior hockey with the Cornwall Royals of the QMJHL in which he scored 63 goals in 64 games, MacDonald was selected 86th overall by the Los Angeles Kings in the 1973 NHL Amateur Draft.
After a sluggish start to the 1975–76 campaign, he was dealt to the Indianapolis Racers, where he rediscovered his scoring touch and finished the year with a career-high 26 goals.
With just six penalty minutes all season, he finished fourth in balloting for the Lady Byng Trophy as the league's most gentlemanly player, an award ultimately won by Gretzky.
MacDonald continued to produce well in 1980–81, but ultimately lost his place on the Oilers' top line with the development of talented young players like Mark Messier, Glenn Anderson, and especially Finnish star Jari Kurri, who would form the most lethal scoring duo in the league with Gretzky for most of the 1980s.
Despite scoring fairly regularly when in the Canucks' lineup, MacDonald would have a tumultuous tenure in Vancouver where his lack of grit and defensive play failed to endear him to the coaching staff.