He was appointed as an assistant coach in 1961 and became head coach a few years later. Miller developed the school's football program, winning consecutive Division II football championships as part of 31 conference wins. After Miller was appointed athletics director, Texas State became a Division I team. He was football coach for 15 years, the second longest term at Texas State and has the best record at 94-53-3.
Miller retired as athletics director at Texas State in 1992.