She first served as a Toronto school board trustee in 1942. At the height of the war she pushed for daycare for the children of women helping with the war effort for free meals for impoverished children. She was elected to Toronto City Council in 1946. She represented Ward 2 which was a mixed area west of the Don River. The northern part of the riding was Rosedale, the wealthiest part of the city. The southern part was Cabbagetown, then one of the poorest neighbour hoods.
On the council she pushed for women's rights, most notably on improving access to birth control. She was also an advocate for the poor and for more social housing, including strong support for the Regent Park project that was built in her ward in the era. In honour of her efforts a Toronto Community Housing Corporation building at Dundas and Broadview was named the May Birchard Apartments.