She received her Equity card while on a regional tour of "A Chorus Line" at the Gateway Playhouse and began to pursue acting, but she also earned money by working as a nanny.
She was nominated for a Helen Hayes Award for Best Actress in a Regional Performance for her role in Wicked, but lost to then co-star Stephanie J.
Kassebaum left the tour in September 2006 after spending a year and a half in the role and was replaced by Megan Hilty.
Kassebaum played "Amy" in the Seattle production of the Stephen Sondheim musical Company at the 5th Avenue Theatre, starring alongside actor Hugh Panaro.
[1] On January 9, 2007, Kassebaum reprised her role as Glinda in the Broadway production of Wicked, replacing Kate Reinders, alongside her former co-stars Julia Murney, Sebastian Arcelus, David Garrison, and Logan Lipton.
[2][3] Kassebaum appeared as Lorraine in the Adam Bock play The Receptionist with former Wicked co-star, Jayne Houdyshell.
[11] Kassebaum played the role of Sam in the musical Leap of Faith, opposite Brooke Shields and Raul Esparza at the Ahmanson Theatre, for an out-of-town tryout running from September 11 through October 24, 2010.
The show was staged at the Moore Theatre, and also included Alice Ripley as Margaret White and Keaton Whittaker as the titular teenager.
Kassebaum then starred in the roles of Mother and Donna Sheridan in the 5th Avenue Theatre's productions of Ragtime and Mamma Mia!, respectively.