Answer by taking a quote from the following article:

O'Donnell, the third of five children, was born and raised in Commack, Long Island, New York. She is the daughter of homemaker Roseann Teresa (nee Murtha) and Edward Joseph O'Donnell, an electrical engineer who worked in the defense industry. O'Donnell's father had immigrated from County Donegal, Ireland, during his childhood, and her mother was Irish American; O'Donnell was raised Roman Catholic. Her older brother is Daniel J. O'Donnell, now a member of the New York State Assembly.

O'Donnell toured as a stand-up comedian in clubs from 1979 to 1984. She got her first big break on Star Search, explaining on Larry King Live: I was 20 years old, and I was at a comedy club in Long Island. This woman came over to me and she said, I think you're funny. Can you give me your number? My dad is Ed McMahon. I was like, yeah, right. I gave her my father's phone number. I was living at home, I'm like, whatever. And about three days later, the talent booker from Star Search called and said, we're going to fly you out to L.A. [...] I won, like, five weeks in a row. And it gave me national exposure. After this success, she moved on to television sitcoms, making her series debut as Nell Carter's neighbor on Gimme a Break! in 1986. In 1988, she joined music video station VH1's lineup of veejays. She started hosting a series for VH1, Stand-up Spotlight, a showcase for up-and-coming comedians. In 1992, she starred in Stand By Your Man, a Fox Network sitcom co-starring Melissa Gilbert. The show bombed, just as O'Donnell's movie career took off. O'Donnell made her feature film debut in A League of Their Own (1992) alongside Tom Hanks, Geena Davis, and Madonna. She was originally considered for the role of Mary Sanderson in Disney's Hocus Pocus, but it was ultimately given to Kathy Najimy. O'Donnell claimed on her blog that she turned down the offer to work with Bette Midler because she refused to portray a frightening evil witch. Throughout her career, she has taken on an eclectic range of roles: she appeared in Sleepless in Seattle as Meg Ryan's character's best friend; as Betty Rubble in the live-action film adaptation of The Flintstones with John Goodman, Elizabeth Perkins and Rick Moranis; as one of Timothy Hutton's co-stars in Beautiful Girls; as a federal agent comedically paired with Dan Aykroyd in Exit to Eden; as the voice of a tomboyish female gorilla named Terk in Disney's Tarzan; and as a baseball-loving nun in M. Night Shyamalan's Wide Awake.

what did she do after star search?
she moved on to television sitcoms, making her series debut as Nell Carter's neighbor on Gimme a Break!