She is known for her roles as Taylor Townsend on the Fox series The O.C., Lizzie Grant on HBO's Entourage, Katie Andrews on ABC's No Ordinary Family, and Leslie Bellcamp on E!

[3] Early in her career, she appeared in television commercials for Burger King, Clean & Clear and International House of Pancakes.

[8][9] First appearing in the show's sixth season, Lizzie is a junior agent working in the Miller Gold Agency's TV division under Andrew Klein, with whom she has an affair.

[10] The show centers on the Powells, a typical American family living in fictional Pacific Bay, California, whose members gain special powers after their plane crashes in the Amazon, Brazil.

[11] She had guest roles in several television shows, including It's Always Sunny In Philadelphia, Ghost Whisperer, Pushing Daisies, Human Target, Royal Pains, Jane by Design, and Hart of Dixie.

[13] The series follows an unknown actress who, after a successful audition, is plucked from obscurity and offered a secret contract to be the fiancée to Kyle West, one of Hollywood's biggest stars.

Reeser has appeared in several feature films and television movies, such as the musical The American Mall with Nina Dobrev, the comedy The Girl Next Door with Elisha Cuthbert, the horror film Lost Boys: The Tribe with Corey Feldman, the thriller The Big Bang with Antonio Banderas, the action movie Smokin' Aces 2: Assassins' Ball with Tom Berenger and the detective comedy So Undercover with Miley Cyrus.

Lacey Chabert as Avery and Allison Sweeney as Tracy were her cohorts, and the three actresses reprised their roles in a sequel trilogy that aired on the Hallmark Channel in 2023.

[23] Since 2006, she has been a member of The WorkJuice Players, a theater troupe primarily known for The Thrilling Adventure Hour, a popular Los Angeles staged production in the style of old-time radio.

In 2015, Reeser and The Thrilling Adventure Hour were invited to perform in New York City and Chicago, then Australia (Sydney) and New Zealand (Auckland and Wellington).

Reeser played the character of Lissette Hanley in the video game Command & Conquer: Red Alert 3, released in 2008.