Published Sunday, 27 October 2013
The TV veteran died on Friday night , according to reports.
As well as her animated role on The Simpsons, Wallace was a regular game show panellist on programmes such as Hollywood Squares and the Match Game, and she also starred on The Bob Newhart Show and appeared on ALF and Murphy Brown.
Sources told TMZ.com that Wallace had been unable to work on The Simpsons for several weeks due to health issues - but producers were still planning a major storyline for her teacher character, for which she won an Outstanding Voice-Over Performance Emmy Award in 1992.
Reports suggested she died from complications related to breast cancer.
Paying tribute to her, The Simpsons executive producer Al Jean said: "She was beloved by all at The Simpsons and we intend to retire her irreplaceable character.
"You fall in love with these people when you see them as characters on television, but when met Marcia you loved her even more. She was sweet, funny, not at all pretentious."