In the 1990s, Stephenson was appointed as a board member on the province's new Education Quality and Accountability Office, which monitors and reports to the public on the performance of the education system. From 1997 to 2005, she was chair of the Learning Opportunities Task Force. and was involved with the Gwillimbury Foundation in its attempt to build a university in Queensville, Ontario. She is a founding member of the Canadian Institute for Advanced Research and also served on the boards of the Ontario Innovation Trust and on the police services board overseeing the Ontario Provincial Police.