Gruenwald ran for a seat to the Alberta Legislature in the 1971 Alberta general election. He ran for a second term in office in the 1975 Alberta general election but was defeated in the three way race by Progressive Conservative candidate John Gogo after his popular vote collapsed, he finished a distant second place.
He won the new electoral district of Lethbridge-West by a wide margin defeating two other candidates to pick it for the Social Cr party who had been defeated from government in that election.
He served as a member of the Legislative Assembly of Alberta from 1971 to 1975 sitting with the Social Cr caucus in the official opposition.
