For the most part, O'Leary has stuck to television in his post-Home Improvement acting career. The bulk of these guest appearances have been one-off roles, including those for popular shows such as Sabrina the Teenage Witch, Numb3rs, The West Wing, and Law & Order: LA.
In a more extensive guest role in 2003, he had a five-episode arc playing Phil Kavanagh on Karen Sisco, a crime drama about the life and work of the titular character (Carla Gugino), a U.S. Marshal living in Miami. More recently, in 2020, he had a three-episode arc as Sgt. Rucker on the Showtime comedy-drama Shameless.
His most extensive TV arc after Home Improvement, however, was on Kamen Rider: Dragon Knight, the show about a parallel dimension called Ventara where young warriors fight the evil alien, General Xaviax. O'Leary played none other than Xaviax himself, appearing in 34 of the 43 episodes.
