[3] For two-and-a-half seasons from 2015 to the spring of 2017 he worked with the tight ends, running backs, wide receivers, and quarterbacks.
[7][8] In 2018, McCullough joined East Central University as the special teams coordinator and quarterbacks coach.
[19] On December 22, 2022, less than two months after becoming full-time head coach for East Central, McCullough was hired by the University of Texas Permian Basin to be the team's second head coach all-time, replacing Justin Carrigan who left to take a role in the athletics department.
[20] In McCullough's first game with the Falcons, he outscored NAIA opponent Texas College 96–0, a program record, and just four points away from the century mark.
[21] The following week the team fell to non-conference opponent Western Colorado before once again scoring 80-plus and beating Southwest Baptist 86–7.
[31] The Falcons would finish the regular season at 10–1, going 8–0 in conference play to win the LSC championship for the first time in program history.
[32] The historic season would continue as UTPB was selected for the NCAA Division II playoffs for the first time in program history, hosting, and losing to, Bemidji State in the first round.
The new contract made him among the highest paid head football coaches in the Lone Star Conference.