Career
Lee started performing at a young age. In 1920 at the age of 10 she performed as an impersonator as an opening act at a local movie theatre. Lee began acting at a late age.
Her first role was 2 March 1965 in an episode of Canadian Broadcasting Company-television"s "Eye Opener", "The Trial of Joseph Brodsky".
Her first regular role was as Maggie Hatch in the television show Hatch"s Mill, which aired for a short time in 1967. Her second television role was in the 1969 television show Strange Paradise.
In 1969, Lee starred in her first film The First Time. Her other movies include My Side of the Mountain, Change of Mind and she played Ma Cobb, the mother of psychotic serial killer Ezra Cobb in the 1974 film Deranged alongside Roberts Blossom.
The Toronto Public Library holds the Cosette Lee collection from 1911, 1920–1976, which contains programs, press clippings, photographs, correspondence, scripts, business papers, documents from professional organizations, memorabilia, all in 3 boxes and 812 items.