O'Reilly, 53, took the BBC to an employment tribunal claiming age and sex discrimination after she was one of four female presenters, all in their 40s or 50s, who were dropped from the 23-year-old show.
The tribunal upheld her claim for age discrimination but not sex discrimination. It also upheld O'Reilly's claim for victimisation.
O'Reilly claimed she was hounded out of the corporation after she was unfairly blamed for newspaper stories criticising the corporation for dropping middle-aged women presenters.
The presenter, who will now receive damages from the corporation as a result of today's verdict, told MediaGuardian.co.uk: "Words cannot describe how happy I feel. It's historic and it's going to have huge implications for all broadcasters."
O'Reilly was dropped from the show, along with Charlotte Smith, Juliet Morris and Michaela Strachan, when it was moved from Sunday mornings to a new peak-time slot in April 2009.
Accusations of ageism have previously been levelled at the BBC over the departure of other high-profile presenters including Arlene Phillips, who was dropped as a judge on BBC1's Strictly Come Dancing but returned as a panellist on a new BBC1 talent show format.
Article from The Guardian