Mtre Marie Legault was President of the Valleyfield Chamber of Commerce in 1989-1990 and 1990-1991, Vice-President of the Valleyfield tourism bureau, and Vice-President of the Valleyfield Economic Development Corporation. She sits on the board of directors of the Centre hospitalier régional du Suroît and of the foundation of the same hospital centre.

She is also a member of the board of the SOLIDE and the investment comity of the Centre Local de Développement.

She is interim President of the Liberal Party Association for the riding of Beauharnois and also sits on the executive of the party.