Marcia Karen Wallace was an American character actress, comedienne and game show panelist, primarily known for her roles in television situation comedies. She is perhaps best known for her roles as receptionist Carol Kester on the 1970s sitcom The Bob Newhart Show, and as the voice of elementary school teacher Edna Krabappel on the animated series The Simpsons, for which she won an Emmy for Outstanding Voice-Over Performance in 1992.

Marcia's caregiver told TMZ ... the actress passed away at home with her family by her side. We're told she had been sick for the past few months ... but the caregiver couldn't go into specifics.

Wallace has been on TV since the 70's -- and spent 3 decades on various game show panels like "Hollywood Squares", "The $25,000 Pyramid" and "Match Game" ... as well as receptionist Carol Kester on "The Bob Newhart Show."

The actress was also a huge activist for breast cancer ... after being diagnosed with the disease in 1985.