Showtime's "Masters of Sex" isn't premiering until September 29, but the drama keeps adding big names.

It was announced that Emmy winner Allison Janney will appear in 5 episodes of "Masters of Sex" playing Margaret Scully, wife of Barton Scully (Beau Bridges), the university provost under whose watch William Masters (Michael Sheen) and Virginia Johnson (Lizzy Caplan) are doing their groundbreaking research into human sexuality.

Production is currently underway on "Masters of Sex," so it won't impact a busy schedule for Janney that also includes co-starring in CBS' Anna Faris comedy "Mom." the "West Wing" star appeared in the recent Sundance film "Touchy Feely."