Over the following years Maggie, under her stage name Maggie Grace, had guest appearances on several television shows, including CSI: Miami, Law & Order: Special Victims Unit and Oliver Beene, and portrayed Martha Moxley in the television movie Murder In Greenwich. In 2003, she played the Goth-influenced, estranged daughter of Tom Selleck and Wendy Crewson in the drama 12 Mile Road.

It was in 2004 that Grace landed her big break when she won the role of the affluent, lazy and self-centered Shannon Rutherford on J. J. Abrams' television pilot Lost. When Lost was picked up for a full season by ABC Grace relocated to Oahu, Hawaii where the show is filmed.

During the hiatus between the first and second seasons of Lost, Grace starred in the remake of the John Carpenter horror film, The Fog, alongside Tom Welling and Selma Blair. The film was nearly universally-panned upon its release that fall. She returned to Oahu for Lost's second season, where she filmed the first six