Ross belonged to the Parti bleu and was elected to the Legislative Assembly of the Province of Canada for the district of Champlain in 1861. He was re-elected in 1863 and served until 1867. From 1873 to 1874, 1876 to 1878 and 1879 to 1882, Ross served as Speaker of the Legislative Council, of whom he remained a member until his death in 1901.
He was Minister without Portfolio from 1876 to 1878 and from 1879 to 1881, as well as the seventh Premier of Quebec from January 23, 1884 to January 25, 1887,
Ross successfully ran as a Conservative candidate for the district of Champlain in the 1872 federal election, but did not run for re-election in the 1874.
He was appointed to the Senate of Canada for the Division of Louisiana Durantaye in 1887 and served as Speaker of that institution from 1891 to 1896. Ross also was Minister without Portfolio in the federal Cabinet for a couple of months in 1896.
He lost the 1886 provincial election as Leader of the Conservative Party of Quebec, but remained in power in a minority government until he resigned on January 25, 1887. He died in 1901 in Quebec City.
Ross was elected to the newly established Legislative Assembly of Quebec for the district of Champlain in 1867, but resigned only a few months later to become a Conservative Member of the Legislative Council of Quebec for Shawinigan.