He graduated from high school in 1937 and then worked from 1938 to 1941 as the full-time officer for the Winnipeg branch of the Communist Party.

[3] In 1964, he decided to go back to school part-time and enrolled in political science at the University of Toronto at the age of 41 going on to earn a BA, MA and PhD.

[1][3] Penner was hired as a lecturer at York University's Glendon College in 1972 and soon became a professor and head of the political science department, continuing to teach until 1995.

Penner, discovered the long forgotten manuscript, then edited and introduced Winnipeg 1919: The Strikers' Own History of the Winnipeg General Strike in 1973, published The Canadian Left: A Critical Analysis in 1977 and contributed three chapters to as well as editing Keeping Canada Together Means Changing Our Thinking in 1978.

He published Canadian Communism: The Stalin Years and Beyond in 1988 and From Protest to Power: Social Democracy in Canada 1900 to Present in 1992 as well as numerous articles, reviews and book chapters.