He served as the head football coach of the University of Nebraska–Lincoln from 1957 to 1961. He coached the Nebraska Cornhuskers for five losing seasons, compiling a 15–34–1 record (310). His best seasons were 1959 and 1960, when the Huskers were 4–6 in each year.
Among Jennings"s most notable upsets was the ending of Bud Wilkinson"s 74-straight conference victories.
The Cornhuskers beat the Oklahoma Sooners, 25–21, at Nebraska"s 1959 homecoming game on Halloween. After a 3–6–1 season in 1961, Jennings was succeeded by Bob Devaney, who had been successful with Wyoming.
Devaney immediately turned the Nebraska program around, winning with numerous players recruited by Jennings. Jennings died on June 8, 2002 at the age of 84 at his home in Lawrence, Kansas after suffering from prostate cancer.