Stanley Morel Cosgrove was born in 1911 in Montreal, Quebec. He studied at the École des beaux-arts in Montreal from 1929 to 1936, and attended drawing classes at the Art Association of Montreal under Edwin Holgate from 1936 to 1938. Around this time he painted in the Gaspé and Charlevoix regions of Quebec.

In 1939, Cosgrove had his first solo show at the École des beaux-arts de Québec, and also exhibited with the Contemporary Arts Society and the Musée du Québec. At the end of 1939 Cosgrove travelled to New York, then on to Mexico, where he studied from 1940 to 1944, notably working on fresco painting under José Clemente Orozco. Upon his return to Canada, he took up a part-time teaching position at the École des beaux-arts in Montreal, and in the following years participated in numerous exhibitions. He was exclusively represented by Dominion Gallery, joined the Canadian Group of Painters, and was elected to the Royal Canadian Academy of Artists. He traveled to France and Spain with fellow artist William Goodridge Roberts in 1953 on a Government Fellowship, where he studied and painted for two years. In 1962 he moved to La Tuque in north-central Quebec for five years, followed by Coaticook for three years, before returning to Montreal in 1970.

In 1985 he retired from teaching to devote his full attention to painting. His works centered on the human figure, still life and landscape, and he is particularly known for his paintings of trees, which the artist stated were not so much trees, but verticals and horizontals on a forest background. He died in 2002 in Montreal. Cosgrove is represented in the collections of the National Gallery of Canada, the Art Gallery of Ontario, the Mendel Collection, Saskatchewan, and the Museum of Modern Art, New York, among others.