2005 and 2008, Joosten won an Emmy for Outstanding Guest Actress - Comedy Series for her portrayal of Karen McCluskey in Desperate Housewives. It was not until the mid-1990s that Joosten made the move to Hollywood, where she took guest roles in television series such as Roseanne, Home Improvement, Picket Fences, Murphy Brown, ER, Seinfeld, Frasier, Just Shoot Me!, Buffy the Vampire Slayer, Dharma & Greg, Las Vegas and The Drew Carey Show. In the 1997 episode of Frasier, 'Roz's Turn', Joosten appeared as Vera, the mother and personal secretary of Frasier's conniving agent, Bebe Glazer, played by Harriet Sansom Harris. The pair would later be reunited to play opposite neighbors in Desperate Housewives.

In 1999, Joosten took the role for which she is best-known, as Delores Landingham, secretary to President of the United States Josiah Bartlet (played by Martin Sheen) in The West Wing. Joosten played the role for two seasons, until her character's death in a car crash in 2001. She would return to the show twice more in flashback episodes.


Joosten's role on The West Wing gave her an entrance into more significant guest roles on significant television series. Since 2001, she has appeared on TV in such shows as Scrubs (appearing in "My Old Lady", which won a Humanitas Prize as well as reappearing in two later episodes), My Name is Earl, Spin City, The X-Files, Judging Amy, Monk, Charmed, Will & Grace, Malcolm in the Middle, Grey's Anatomy, The Suite Life of Zack and Cody, Reba, So Little Time, Gilmore Girls, The Closer and a recurring role as one of the less intimidating incarnations of God seen by the title character (played by Amber Tamblyn) on the TV series Joan of Arcadia.

In 2005, Joosten appeared in the film Wedding Crashers, starring Vince Vaughn and Owen Wilson. Joosten also has a recurring role on Desperate Housewives as Karen McCluskey. For this role, Joosten won two Emmy Awards for Outstanding Guest Actress in a Comedy Series in 2005 and 2008 and once again got nominated for 2010, and appeared as a presenter at the 2005 and 2008 Emmy Awards telecasts. She also received Screen Actors Guild Award nominations with the rest of the cast for Outstanding Performance by an Ensemble in a Comedy Series from 2006-2008. She was promoted to a member of the regular cast in Season 6. However, the Emmys still billed her as a "Guest Actress" when she was nominated for a third time for Outstanding Guest Actress in a Comedy Series for the 2010 Emmys. She then played Aunt Jackie in Alvin and the Chipmunks: The Squeakquel in 2009.

In 2009, Joosten and Lily Tomlin were in talks to star in a Desperate Housewives spin-off.[3] The spin-off was given a preliminary green light to proceed.[4] However, the series did not proceed.