(written from a Production point of view)
O'Hara began his career in show business as an actor. He appeared on an episode of Kate Mulgrew's short-lived series Mrs. Columbo, an episode of The Greatest American Hero with James Saito, and the pilot episode of the short-lived NBC time travel series Voyagers!, with Ed Begley, Jr. He also had roles in the films Something Short of Paradise, The Devastator, and Naked Vengeance. The first project O'Hara directed was the 1988 independent film Darkroom, after which he moved on to television.
O'Hara has directed numerous episodes of the television series Dr. Quinn, Medicine Woman, Silk Stalkings, Touched by an Angel, The Pretender, JAG, Angel, Smallville, NCIS, and CSI. The actors he has worked with on these shows include Chad Allen, Barbara Babcock, John Berg, Corbin Bernsen, John Billingsley, Michelle Bonilla, Charlie Brill, Dennis Christopher, Bill Cobbs, Robert Costanzo, Steven Culp, Tim de Zarn, Michael Dorn, Cully Fredricksen, John Glover, Gary Graham, Bruce Gray, Brad Greenquist, Pat Healy, Gregory Itzin, Georgann Johnson, Leslie Jordan, Jack Kehler, Sally Kellerman, Patrick Kilpatrick, Jeff Kober, Clyde Kusatsu, Joe Lando, Wallace Langham, Ed Lauter, Scott Lawrence, William Lucking, Scott MacDonald, Kenneth Marshall, J. Patrick McCormack, Zoe McLellan, Glenn Morshower, Mark Moses, Enrique Murciano, Jeffrey Nordling, Randy Oglesby, Terry O'Quinn, Robert O'Reilly, Robert Pine, Harve Presnell, Jeremy Roberts, Andrew Robinson, Daniel Roebuck, John Rubinstein, Jennifer Savidge, Michael Buchman Silver, Mike Starr, Maury Sterling, Dean Stockwell, Gail Strickland, Keith Szarabajka, Susanna Thompson, Helene Udy, Steve Vinovich, Michael Welch, Debra Wilson, Michael Wiseman, and Sam Witwer.
In addition to Voyager, O'Hara has directed for such science fiction series as Dark Angel (starring John Savage), The X-Files (the 2001 episode "Surekill" with Patrick Kilpatrick and Kellie Waymire), and Heroes (the 2007 episode "The Fix" with Zachary Quinto and George Takei). He also directed three episodes of the CBS series The Unit, starring Star Trek: Enterprise guest actress Abby Brammell. He more recently directed two episodes of Shark, the hit CBS crime drama starring Voyager actress Jeri Ryan.