The stage trained actor, with several productions to his credit in both New York and Los Angeles, began to receive greater offers for featured acting roles following his impressive performance in the smart horror flick "Scream". Lillard starred opposite Sean Astin in "Dish Dogs" (1998), the pair playing road travelers who pay their way washing dishes. 1998 also saw the actor with a co-starring role in the sophomoric comedy "Senseless" and a featured part in the biopic "Without Limits" as Roscoe Devine, a friend of Olympic runner Steve Prefontaine. That same year, Lillard starred in the home video hit "The Curve" as an ambitious college man bent on killing a fellow student in a bid to receive the legendary automatic 4.0 given to roommates of suicide victims.

The actor's career continued on this upward trajectory through 1999, beginning with his lively and memorable performance in the featured role of Brock, a moronic and egomaniacal former "Real World" cast member who wins the heart of Freddie Prinze Jr.'s spiteful girlfriend in the hit teen comedy "She's All That". Later that year, Lillard reteamed with Prinze in the less successful action film "Wing Commander", based on the popular video game. While reviews praised the performances of the cast members, the film received lackluster notices and box office returns. He also starred in the charming "SLC Punk!", as the blue mohawk sporting Stevo, a likable Utah punk faced with a higher education moral dilemma: whether or not to accept an invitation to study at Harvard Law School, a sure sign of selling out given his commitment to the hardcore lifestyle. Following this strong performance, Lillard starred in Kenneth Branagh's adaptation of "Love's Labour's Lost" (2000). Set as a 1930's musical, the film, while providing Lillard with his greatest acting challenge thus far, also required him to sing.

Before pursuing a film career, Lillard hosted the Nickelodeon skater sports show "SK8 TV" (1989). Other small screen projects of note include his TV-movie debut in 1994's syndicated "Vanishing Son IV", and his work as an over-the-edge man who shoots up an abortion clinic in the "1996" segment of "If These Walls Could Talk" (HBO, 1996), directed by and starring Cher. Additionally, Lillard also appeared alongside Kim Delaney in the 1997 ABC thriller "The Devil's Child". In 1999, Lillard gave an impressive performance as a brilliant disillusioned teen imersing himself in the 1980's punk culture, in "SLC Punk." The movie opened to positive reviews at Sundance and remains a cult classic for its probing look at a little known subculture. Lillard next appeared with Alicia Silverstone in a musical remake of the Shakespeare classic "Love's Labour Lost." (2000). Lillard returned to do a series of more mainstream fare, appearing with Shannon Elizabeth in 2001's "Thirteen Ghosts" and then as Shaggy in the teen dream cast for "Scooby-Doo" (2002) and its 2004 sequel, as well as the teen S.A.T. key-stealing caper "The Perfect Score" (2004). The actor next attempted to break out of sidekick roles by carrying--along with Seth Green and Dax Shepherd--the sometimes hilarious great outdoors comedy "Without a Paddle" as a burnt-out business exec who conspires with his pals to discover bank robber D.B. Cooper's lost stash of cash. Next it was back tom familiar "best friend" territory, this time to Josh Hartnett in the steamy thriller "Wicker Park" (2004).