Clarke has been cast as the mother of Sam Evans, played by returning cast member Chord Overstreet. She will appear in the Dec. 6 episode and may become a recurring character.
As previously reported, John Schneider (Chicago, Grand Hotel) has been cast as Sam's father and will appear in the season's eighth episode.
Clarke has been seen on Broadway in I'm Not Rappaprort and Off-Broadway in The Director. Her film and television credits include "American Horror Story," "The Defenders," "Guiding Light," "A Beautiful Mind" and "One Life to Live," among others.
"Glee" airs Tuesday nights on Fox at 8 PM ET.