He worked hard to obtain projects for his community including the construction of bridges, lighthouses and the establishment of a ferry service.
Marcil was nominated for the position of Speaker by Wilfrid Laurier following the 1908 election. Despite initial opposition by OntarioTories, he was unanimously elected to the position.
He was a popular Speaker and might have continued through a second Parliament had the Liberals not been defeated in the 1911 election. He returned to the backbenches, and concurrently was elected to sit on Montreal's city council as an alderman in 1918 while remaining an MP.
From 1921 to 1931, he served as Chairman of the Liberal caucus in Ottawa. He was Dean of the House from 1930 to his death in 1937.
Charles Marcil was not the only member of his family to be involved in politics. In the late 19th Century, his uncle Doctor David Marsil was mayor of Saint-Eustache, Quebec from 1871 to 1875 and appointed to the Legislative Council of Quebec in 1888. Charles Marcil's brother Georges was the last mayor of Notre-Dame-de-Grâce, before the city was annexed to Montreal in 1910. Georges' granddaughter Susie Marcil was married to Daniel Johnson, Premier of Quebec in 1994.