In 1970 she returned to the University of Montreal with the intention to learn from Serge Garant.In 1971, Vaillancourt joined the faculty of music at the University of Montreal.
From 1971 to 1973, she worked with Bruce Mather and Serge Garant; in 1974, she became director of the University of Montreal's contemporary music workshop, replacing Mather.
From 1972 to 1975, she worked at the Atelier-laboratoire of the University.
In 1989, she founded the Nouvel Ensemble Moderne, the ensemble-in-residence at the faculty of music at the University of Montreal, which has received numerous awards.