Grégoire ran for mayor in Quebec City in 1934 and won, defeating Pierre Bertrand.

He was elected as the Action libérale nationale candidate to the Legislative Assembly of Quebec in 1935 in the riding of Montmagny.

In 1937, he and colleagues René Chaloult, Oscar Drouin, Philippe Hamel and Adolphe Marcoux left the Union Nationale.

In the 1935 New Year Honours, he was made a Commander of the Order of the British Empire.

This article about a Member of the National Assembly of Quebec from the Union Nationale is a stub.