O'Neil was a semi-regular cast member of Coronation Street in the mid-1960s as Ruth Winter, and also made frequent guest appearances in series such as Z-Cars, Dixon of Dock Green, Adam Adamant Lives!, No Hiding Place and Softly, Softly.
[2] She was also a leading cast member in the drama series The Standard[3] and The Spoils of War.
She played the role of Eleanor, Duchess of Gloucester, in the BBC television version of The Wars of the Roses.
[4] She latterly appeared in Taggart, Lovejoy, Hamish Macbeth, Heartbeat, Peak Practice, Holby City, Monarch of the Glen and Bad Girls.
[5] She also appeared as Hannah Sempel, the "keeper of the keys", in the BBC Radio drama "McLevy" alongside Scottish actors Brian Cox and Siobhan Redmond.