[3] In 1968, Wonham proved a separation theorem for controls in a more general cost functional class with many technical assumptions and restrictions.

[4] Wonham returned to Canada in 1970, after fifteen years away, and joined the University of Toronto as an associate professor in the Faculty of Electrical Engineering.

[3] Wonham and his student Bruce Francis first articulated the internal model principle in 1976, which is a good regulator restricted to the ordinary differential equations subset of control theory.

In 1987, Wonham and Peter Ramadge introduced supervisory control theory as a method for automatically synthesizing supervisors that restrict the behavior of a plant such that as much as possible of the given specifications are fulfilled.

[7] Wonham authored and co-authored about seventy-five research papers, as well as the book Linear Multivariable Control: A Geometric Approach.