He served as the interim head football coach at University of Wisconsin–Madison for one season in 1986, compiling a record of 3–9.
He returned to Warren in 1966 as defensive coordinator before being promoted to head coach in 1970 at Western Reserve High School.
During his six seasons, Hilles helped Ball State join the Mid-American Conference in 1973, achieve NCAA Division I status in 1974, and was defensive coordinator of the 1976 MAC championship team.
Hilles continued to be the defensive coordinator and inside linebackers coach on Dave McClain's staff at the University of Wisconsin–Madison (1978–1985).
After McClain's death on April 28, 1986, Hilles was named interim head football coach for the 1986 season.