In 1994, Bosio had a 4–10 record with 4.32 ERA in 19 games (all starts). His record improved to 10–8 in 1995, when he played in 31 games (all starts) and had a 4.92 ERA. Bosio's only postseason appearances were in 1995. He started two games in the ALDS against the New York Yankees, pitching a total of innings and giving up nine earned runs (10.57 ERA); he did not record a win or a loss. Seattle advanced to the ALCS, losing in six games to the Cleveland Indians. Bosio started Game 5, giving up three runs (two earned) in innings and taking the loss.