Margaret was born in Worthington, Ohio. She dropped out of high school to move to Los Angeles with her mother after her parents' divorce. While struggling financially, she landed her first role as the title character in the web-based video series Rachel's Room in 2001. She went on to earn a Young Artist Award nomination in 2002 with her portrayal of 15-year-old murder victim Martha Moxley in the television movie Murder in Greenwich. In 2004, Grace was cast as Shannon Rutherford in the television series Lost, on which she was a main cast member for the first two seasons, winning a Screen Actors Guild Award shared with the ensemble cast. Leaving the series, Grace was keen to work more prominently in film having starred opposite Tom Welling in The Fog in 2005. She appeared in Suburban Girl, The Jane Austen Book Club (both 2007), and Taken (2008). She has the lead role of Alice in Malice in Wonderland, a modern take on Lewis Carroll's novel Alice's Adventures in Wonderland. Grace reprised the role of Shannon in two more episodes of Lost, including the series finale.
Maggie reprised her lead role in Taken 3 (2014) opposite Liam Neeson. She saw tremendous success with Taken - Revenge (2012) that has earned $131,300,000 at the domestic box office and $348,351,000 worldwide since its October 2012 release. Maggie also starred as one of the leads in "About Alex", which had its premiere in Tribeca in 2014 and as the lead in Simon Helbergs comedy "We'll Always Have Paris" which premiered at SXSW. She also appeared in "Decoding Annie Parker", opposite Aaron Paul and in the role of "Irina" in the final installment of the Twilight franchise, "Twilight: Breaking Dawn", for Summit Entertainment. Maggie has also starred on Broadway in William Inge's Pulitzer Prize-winning "Picnic" directed by the Tony nominated director Sam Gold as well as an arc on the last season of Showtime's Californication (2007).
Maggie was named one of Variety's Top 10 Actors to Watch. Her other credits include James Mangold's "Knight & Day" opposite Tom Cruise and Cameron Diaz for Fox and Robin Swicord's "The Jane Austen Book Club" alongside Maria Bello and Emily Blunt.
- Still has the same car she bought when she was 18.