Primarily a supporting player in TV and movies, although she did star opposite Larry Hagman in NBC's "The Return of the World's Greatest Detective" (1976), O'Hara portrayed Emily Mahoney during the first season (1979-80) of "The Facts of Life" (NBC) and was a series regular as Pam Dawber's loyal assistant on "My Sister Sam" (CBS, 1986-87). Numerous guest spots on series like "Murphy Brown", "Law & Order", "ER" and "The Drew Carey Show" preceded her landing the regular role of Lottie, Sue Murphy's tough, unsentimental working class mother in the short-lived Fox sitcom "Costello" (1998). Among her feature film credits are "Heart Beat" (1979, her debut), "Angie" (1994, with Geena Davis) and "Wes Craven's Wishmaster" (1997). O'Hara also enjoyed a recurring role on CBS' daytime drama "As the World Turns", paired opposite her writer-actor husband Nick Ullett.