In May 2011, The CW renewed the series for its ninth and final season which Colletti maintained his regular status.
In January 2007, Colletti was announced to have been cast in a major recurring role on The CW teen drama television series One Tree Hill.
Colletti portrays the role of Chase Adams, a high school student who plans to save himself till marriage.
Over the course of the following seasons Colletti maintained a major recurring role.
In November 2010, Colletti was confirmed to have been upgraded as a core series regular for the series eighth season.
Colletti was born in Newport Beach, California, the youngest child of Lorilee (née Goodall) and Bruce Colletti.
Colletti has an older brother John, and an older sister Lauren.As a teen, Stephen attended Laguna Beach High School in Laguna Beach, California. In 2004, MTV commissioned a planned reality television series Laguna Beach: The Real Orange County which followed the lives of wealthy teens and Colletti was asked to appear on the show. Upon graduating high school, he attended San Francisco State University for a year before returning to Los Angeles to pursue an acting career.In 2007 Colletti appeared as himself in an episode of another MTV Reality Television series The Hills."Surprisingly, the producers had a bigger effect, as they controlled and mapped our lives more than we were aware.One of the most hurtful things they did was pressure Stephen to spend time with another girl from the show, Lauren, while he and I were dating.It certainly provided some juicy conflicts, but it also affected me deeply. On one side, it seemed like the producers were trying to break us up, which was intimidating.