O’Leary is no stranger to Division III soccer, having started his career at Elmira (N.Y.) College, where he posted a stellar 38-11-2 mark from 1989-1991. In 1992, he became the head man at Kenyon (Ohio) College, where he posted a 32-4-4 record and led the squad to a berth in the 1993
NCAA Semifinals. After being named the Great Lakes Regional Coach of the Year, he earned his first Division I head job at Dartmouth.

O’Leary guided the Big Green to a 56-48-14 record and two NCAA College Cup appearances in his seven seasons, including a 12-6 record and Ivy League runner-up finish in 2000. Dartmouth was 10-4-4 and reached the second round of the NCAA Tournament in 1997 as O’Leary was named Division I Coach of the Year by the New England Intercollegiate Soccer League.

The Dublin, Ireland native continued to build his reputation at Division I George Mason as the Patriots became contenders in the Colonial Athletic Association during his tenure. His four-year stint was highlighted by an 11-6-6 campaign in 2003, as the team reached double figures in victories for the first time since 1998 and reached the CAA Tournament Championship game.

A gradute of Thomas Edison State College, O’Leary began his coaching career as an assistant coach at Boston College and New Hampshire and holds a NSCAA Advanced National Diploma in addition to his UEFA "A" Level License.