He was a member of the Legislative Assembly of Manitoba from 1958 to 1976, representing the Progressive Conservative Party.
He was re-elected in the elections of 1959, 1962, 1966, 1969 and 1973, on the last two occasions for the redistributed riding of Souris-Killarney.
[2] The only time when his election was in doubt was 1966, when the Liberals ran a strong challenger.
[citation needed] He was not appointed to cabinet by either Dufferin Roblin or Walter Weir.
[2] McKellar was elected as a director of Portage Mutual Insurance in 1973.