[1] He represented the electoral district of Cochrane South in the Legislative Assembly of Ontario from 1943 to 1955 as a member of the Co-operative Commonwealth Federation (CCF).
He had fought in World War I as an officer in the British Army where he saw action in the Mesopotamian campaign.
In the 1943 provincial election he ran as the Co-operative Commonwealth Federation candidate in the riding of Cochrane South.
[2] He was the only CCF MPP to survive both the 1945 and the 1951 provincial elections, which saw most CCFers defeated, including party leader Ted Jolliffe.
[3] Grummett was defeated in the 1955 general election by Ontario Progressive Conservative Party candidate Wilf Spooner, who was mayor of Timmins, Ontario, when the Liberals failed to field a candidate allowing "old party votes" to coalesce around Spooner.