A veteran of over ten years of professional experience in New York theater and commercials, O'Connell made an auspicious feature film debut at age 11 playing the chubby, winsome Vern Tessio of Rob Reiner's "Stand By Me" (1986). While he held his own against such future feature heavyweights as River Phoenix and Kiefer Sutherland, O'Connell found much of his subsequent employment in TV.
After several TV-movies, including a lively adaptation of humorist Jean Shepherd's twisted nostalgic story "Ollie Hopnoodle's Haven of Bliss" (Disney Channel/PBS, 1988), O'Connell landed the lead in the fantasy series, "My Secret Identity" (syndicated, 1988-91). His Andrew Clements was an ordinary teen bestowed with super powers, including the ability to fly, after a run-in with a photon beam. This marked the beginning of O'Connell's regular employment as a TV juvenile lead. After starring in the short-lived "Camp Wilder" (ABC, 1992), O'Connell co-starred with Jason Priestly in the feature "Calendar Girl" (1993), as Scott 'The Dood' Foreman, an eighteen-year-old with a wooden leg. He delivered a solid comic performance in this coming-of-age tale about three boys' search for their idol, Marilyn Monroe.
O'Connell's returned to TV in "Blue River" (Fox, 1995), based on the novel by Ethan Canin. Showcasing his pumped-up physique, the actor believably played both the youthful and middle-aged versions of an unstable man coping with a dysfunctional family. O'Connell also headed the cast of the sci-fi adventure series, "Sliders" for its duration on Fox (1995-97) and one season on the Sci-Fi Channel (1998-99), as a physics grad student who unknowingly creates a doorway to parallel universes. His sculpted body was even more evident when he donned "Rambo" gear to battle some pesky roaches in "Joe's Apartment" (1996). Based on the popular MTV short of the same name, the film featured a lovelorn protagonist whose life is ruined by his "friendly" insect roommates. He also won the coveted role of a football player handled by sports agent Tom Cruise in "Jerry Maguire" (1996) before tackling the part of Neve Campbell's boyfriend in "Scream 2" (1997).
After playing an astronaut in the sci-fi misfire "Mission to Mars" (2000) O'Connell returned to the youth sex-comedy genre with the "American Pie"-wannabe "Tomcats" (2001), an unfunny film which performed poorly. He found a comfortable niche by returning television, however, playing Det. Woody Hoyt on the NBC crime series "Crossing Jordan" (2001 - ). O'Connell returned to the big screen in 2003 as one of a down-on-their-luck duo of losers who run afoul of both the mafia and a troublesome marsupial in "Kangaroo Jack" (2003). After being one of many celebrities to jump aboard the poker bandwagon by appearing on “Celebrity Poker Showdown” (Bravo, 2003- ), O’Connell voiced a character for an episode of “Justice League Unlimited” (Cartoon Network, 2003- ). He then had a supporting role in the romantic comedy “Yours, Mine and Ours” (2005), a remake of the 1968 Lucille Ball-Henry Fonda comedy about two high school sweethearts who reunite after the deaths of their spouses and rush to get married only to discover their children hate the new arrangement.