In the 1983 postseason, McGregor allowed only two runs in the openers of the ALCS and World Series, but lost both games by scores of 2–1 to the White Sox and Phillies, respectively. However, in Game 5, he shut out the Phillies in a complete game to end the series, four games to one. He remained a starting pitcher on the Orioles for the next five seasons, and made his final appearance on April 27, 1988.