Leonard attended the University of Arizona and was a decathlete for the 1964 Olympic trials. Moreover, Terry played professional football for the British Columbia Lions in Vancouver, Canada until his burgeoning football career was abruptly curtailed by a back injury. In the wake of said back injury, Leonard contacted veteran stuntman Chuck Roberson about getting work in Hollywood, California. Terry worked as an extra on the film McLintock! (1963) and performed his first big stunt for the Western movie El Dorado (1966). Leonard subsequently went on to have a long and impressive career as a stuntman, stunt coordinator, and second unit director on a slew of films and a handful of TV shows that have encompassed several decades.

In 2003 Terry was the recipient of a Golden Boot Award for his sterling and significant contributions to the Western genre.