Bellard was a high school head coach for 21 seasons, where he achieved a record of 177–59–9 and won three state titles. During his time as a high school coach, he explored the idea of running an offense out of a three-back formation. Bellard began coaching at Ingleside High School, a Class B school in Ingleside, Texas. He guided the school to two consecutive regional wins in 1953 and 1954, and a street near Ingleside High School is named after him. He was then hired to succeed Joe Kerbel at Breckenridge High School, then a state powerhouse in the second-highest UIL classification. Under coach Kerbel and his predecessor Cooper Robbins, Breckenridge won three 3A state championships in 1951, 1952, and 1954. Bellard continued that winning tradition with state titles in 1958 and 1959. In 1960, Bellard was selected over Gordon Wood to replace Bob Harrell as head coach at Central High School in San Angelo, Texas. San Angelo Central was playing in the highly competitive District 2-4A, nicknamed the "Little Southwest Conference", against perennial state champions such as Abilene and Odessa Permian. Bellard amassed a 59–19–2 record at San Angelo Central, winning a 4A state championship in 1966. He then left the high school ranks for the University of Texas at Austin. In 1988, Bellard returned to the high school level, coaching Spring Westfield High School near Houston, Texas, to a 41–22–5 record over six seasons.
Bellard became head coach at Texas A&M in 1972, taking over head-coaching duties from Gene Stallings. In his seven years at Texas A&M, he finished with a record of 48–27 and three top-15 finishes. Acting as his own offensive coordinator, Bellard hired former high school football coaches to assist him as backfield coaches, including Gil Bartosh and Chuck Moser. Both Bartosh and Moser had won Texas state championships. In 1975, however, Bellard hired Tom Wilson away from Jim Carlen's Texas Techcoaching staff to serve as the Aggies' offensive coordinator. For the defensive department, Bellard hired Melvin Robertson, one of the top defensive coaches, away from Bill Yeoman's coaching staff at the University of Houston. Robertson became defensive coordinator, and among his assistants were R. C. Slocum and Dan LaGrasta. Bellard's first two seasons at Texas A&M were difficult, as his Aggies finished 3–8 and 5–6, respectively. In 1974, with a pair of his own recruiting classes suited to run the wishbone formation, the Aggies went 8–3, then followed it up with two 10–2 seasons, including a pair of wins over Royal and the Longhorns and three consecutive bowl games. After starting the 1978 season 4–0, Bellard resigned mid-season after two consecutive losses: 33–0 to Houston and 24–6 to Baylor.
Mississippi State
After A&M, Bellard spent seven seasons as head coach at Mississippi State University. His best years as the Bulldogs head coach were in 1980 and 1981, when his team finished 9–3 and 8–4, respectively. Also, Bellard was the coach when Mississippi State defeated number 1, undefeated Alabama 6-3 in Jackson, Mississippi in 1980. However, the Bulldogs significantly regressed after 1981. In the next five seasons, he only won a total of five games in SEC play. Before the 1985 season, Bellard boldly predicted that the Bulldogs would rebound and win their first SEC title since 1941. They not only failed to do so, but went winless in SEC play. Bellard was fired after the season.
