Mallory is the Indiana Hoosiers' winningest football coach, having compiled a 69–77–3 record. Before taking over the head coaching reins at Indiana in 1984, Mallory coached three other schools to national prominence. While compiling a 168–129–4 career record, Mallory became one of only a handful of coaches in history to guide three different programs to top 20 finishes in national polls. In 1987, Mallory became the first coach to be awarded back-to-back Big Ten coach-of-the-year honors. While at Indiana, Mallory led the Hoosiers to six bowl games including victories in the 1988 Liberty Bowl, and the 1991 Copper Bowl. He also led IU to a top 20 ranking in 1987 and 1988.
Mallory was the 15th head college football coach for the Northern Illinois University Huskies located in DeKalb, Illinois and he held that position for four seasons, from 1980 until 1983. His career coaching record at Northern Illinois was 25 wins, 19 losses, and 0 ties. This ranks him sixth at Northern Illinois in total wins and seventh at Northern Illinois in winning percentage.