[2] During his MLB career, Aase played with the Boston Red Sox (1977), California Angels (1978–84), and Baltimore Orioles (1985–88), of the American League.

However, he bounced back in 1974 with the Winston-Salem Red Sox, leading the Carolina League in wins, complete games, and shutouts, and was named the circuit's Pitcher of the Year.

He won his first big league game against the Milwaukee Brewers on July 26 and then threw a shutout against the California Angels five days later.

Aase was moved to the bullpen in the middle of the 1980 season (he would never start another big league game after that) and was the Angels primary closer in 1981, notching 11 saves.

In the only All-Star Game appearance of his career, he came on in the ninth inning with runners on first and third and one out, and earned the save by inducing Chris Brown to hit into a game-ending double play.

Aase's sole win in 1987 came on Opening Day, April 6, pitching an inning and a third of scoreless relief after replacing Mike Boddicker.

With the Dodgers trailing the Padres 4–3, Aase replaced Dennis Cook and allowed two unearned runs over one-third of an inning before giving way to Darren Holmes.