Alan Caswell Collier was born in Toronto in 1911 and began to show an interest in art at age 12. From 1929 to 1933 he studied at the Ontario College of Art under J.E.H. Macdonald and Franklin Carmichael. He furthered his studies at the Art Student's League in New York in 1937, working at mines during the summer to fund his education.
In 1939 he found work in New York as an advertising artist, but moved back to Toronto to work as a sheet metal worker in 1942 after marrying fellow Canadian Ruth Brown the year prior. He joined the Canadian Army in 1943, and upon his return from the war in 1946 he again worked as an advertising artist in Toronto, but focused more on his painting and less on his commercial art. His landscapes are known for their well-defined sense of form and strong compositions stripped of extraneous detail.

In 1951 Collier started doing a series of paintings of underground mining, one of which is in the collection of the National Gallery of Canada. He was elected to the Ontario Society of Artists in 1952 and began teaching advertising art at the Ontario College of Art in 1955. The following year marked the first of many summer sketching trips taken with his family to various parts of Canada, including British Columbia. He began painting full time in 1967, and a retrospective of his work was held by the Robert McLaughlin Gallery in 1971. He traveled to the High Arctic to paint with the Polar Continental Shelf Project in 1984 and 1985.

Collier died in Toronto in 1990 at the age of 79. His work is represented in the National Gallery of Canada, the Art Gallery of Ontario, the Robert McLaughlin Gallery and the Frye Museum in Seattle, among many others.