She graduated from Deer Creek High School and also attended Oklahoma City University, graduating with a Bachelor's of Music in vocal performance/opera. O'Hara studied voice with Florence Birdwell, who also taught Broadway star Kristin Chenoweth four years earlier. O'Hara and Chenoweth are both alumnae of the Gamma Phi Beta sorority.
O'Hara played the role of Dot/Marie in the L.A. Reprise! concert staging of" Sunday in the Park with George". She can be heard as the voice of producer Beth Totenbag on PBS's 2008 animated series "Click and Clack's As the Wrench Turns".
From April 24th, 2012 to March 24th, 2013, she is starred on Broadway in "Nice Work if You Can Get It" as Billie Bendix, a role for which she received her fourth tony nomination. She was replaced by Jessie Mueller.
2008 - "Wonder in the World"
2011 - "Always"
2002 Sweet Smell of Success
2003 - "My Life with Albertine"
2005 - "The Light in the Piazza"
2006 - "Harry on Broadway", Act I—two-disc set: 1. Original Broadway cast recording "The Pajama Game"; 2. Songs from Thou Shalt Not, Harry Connick, Jr. featuring Kelli O'Hara
2008 - "South Pacific"
2012 - "Nice Work If You Can Get It"