O'Hara was born in Elk City, Oklahoma, and grew up in an Irish American family. She graduated from Deer Creek High School and also attended Oklahoma City University, graduating with a bachelor's degree in Music in vocal performance/opera. O'Hara studied voice with Florence Birdwell, who also taught Kristin Chenoweth four years earlier. O'Hara and Chenoweth are both alumnae of the Gamma Phi Beta sorority.
- She's a six-time Tony Award nominee
- She received Tony nominations for her performances in The Light in the Piazza, The Pajama Game, South Pacific, and Nice Work if You Can Get It.