Reid occupied high-ranking cabinet positions in Greenfield's government and that of his successor, John Edward Brownlee. Greenfield appointed him Minister of Health and Minister of Municipal Affairs in 1921. In the former capacity, he drew on his past experience with the Vermilion board in establishing new municipal health boards. He also proposed a program of eugenics through the sterilisation of the mentally handicapped, which in 1928 led to the "Sexual Sterilization Act" of Alberta. As an advocate of government-wide economy, he laid off all school inspection nurses and many public health nurses. This inclination towards thrift was also evident in his performance as Minister of Municipal Affairs, in which he resisted a 1926 call from several municipalities to transfer a greater proportion of the responsibility for caring for indigents to the province. In 1929, he disagreed with them again when he insisted that they be responsible for 10% of the old-age pensions paid to their residents.