Reid was born in Whitstable, Kent, England; her father was a doctor in the British Army. She lived in Germany, Africa and the United States before settling in Canada with her family in 1964. She studied acting at McGill University receiving a Bachelor of Arts degree in 1972 and at the Banff Centre for the Arts. Her first professional acting job was a school tour with the Globe Theatre in Saskatchewan. Reid lent her voice in the 1978 Halloween special Witch's Night Out on NBC.
She appeared for three seasons as Cathy on the King of Kensington and was nominated in 1977 for an ACTRA Award for Best Performance in a Continuing Role in a Television Program.She left after expressing a desire to return to the stage.
Her television credits have included Dr. Zonk and the Zunkins,, Coming Up Rosie, P.R., Pearlie and Jacob Two-Two. She also appeared in the films Switching Channels, At the End of the Day: The Sue Rodriguez Story, Duct Tape Forever, My Big Fat Greek Wedding,Prom Queen: The Marc Hall Story and Beethoven Lives Upstairs.
She has been a mainstay on the stage at the Shaw and Stratford Shakespeare Festival. She has twice won the Dora Mavor Moore Award, in 1993 for Fallen Angels and in 1995 for Six Degrees of Separation.
Reid voiced Mrs. Jenkins in the animated series Timothy Goes to School.