In an 11-season career, O'Leary posted a .274 batting average with 127 home runs and 591 runs batted in in 1198 games.
A 13th-round pick in , O'Leary enjoyed a great season at Double-A El Paso, winning the Texas League batting title with a .334 average and stealing 28 bases. O'Leary had batted over .330 twice before. He was promoted to Milwaukee a year later, and after two seasons, he was selected off waivers by the Red Sox.
From -, he collected at least 80 RBI in each season, batting .308 in 1995 and a career-high .309 in . In , he compiled career highs in home runs (28), RBI (103), doubles (36), and finished with a .280 average.
O'Leary is currently working on writing a book about his MLB career.