Why did Mischa Barton leave The O.C.? Updated: 19 May 2021, 21:52 MISCHA Barton appeared on 76 episodes of The O.C., which aired on Fox from 2003 until 2007. The actress opened up about her exit from the popular teen drama in a tell-all interview. 4 Why did Mischa Barton leave The O.C.? Mischa Barton's The O.C. character Marissa Cooper was dramatically killed off during the final episode of season three. She opened up about her departure in an interview with E! News in May of 2021. "I've always felt ashamed in a way to really talk about what went on behind the scenes because I've always been a very private person and very aware of people's feelings," Barton told E! News a phone interview.