O'Donnell graduated from Northwestern University[3] in 1987 with a Bachelor of Science in Education degree, focusing on a combined course of study in journalism and public policy.
She served as a reporter and anchor at WJW TV in Cleveland, Ohio, in the 1990s. At this time, O'Donnell worked with former NBC reporter Martin Savidge when WJW was still a CBS station in Cleveland.[3]
Beginning in 1994, O'Donnell followed a broad range of stories as an NBC News correspondent based in New York City and Los Angeles.[3]
O'Donnell was a regular panelist on The Chris Matthews Show until it was canceled.[4] She had served as news anchor and substitute host on the Weekend Today program and the weekend edition of Nightly News. She has contributed reports to the primetime news magazine Dateline NBC.[3] She served as White House correspondent for NBC News during the second term of George W. Bush; following the 2008 presidential campaign season, she became Capitol Hill correspondent.[3]
O'Donnell was inducted into the Cleveland Journalism Hall of Fame in 2011[7] and the Ohio Radio/Television Broadcasters Hall of Fame in 2004.[3]
She has received the 2014 Alumnae Award and in 2010 the Alumni Merit award from Northwestern University.[8] In 2017, O'Donnell was awarded the Northwestern Alumni Medal—the highest honor given by the Northwestern Alumni Association.[9]
She has received many honors, including Emmy awards, a National Headliner award, a New Hampshire Primary Award for Political Reporting, and Los Angeles Press Club awards.[3]