The 6-foot-9, 300-pound big man had contemplated his college decision throughout the last week, and on the last day of the period on of the nation's top big men went with Oklahoma.
"He signed his papers and sent them in," Gallon's AAU coach Marland Lowe confirmed.
According to Lowe, Oklahoma's coaching staff and future point guard Tommy Mason-Griffin played big roles in his decision.
"He liked the coaching staff," he said. "Coach [Oronde] Taliaferro and coach [Jeff] Capel built a very good relationship with him. Ultimately he really loves playing with Tommy Mason-Griffin and he wanted to play with him in college. This was another great opportunity for him to be able to step right in and play right away."
Gallon, who also considered Mississippi State, is ranked No. 5 on Scout.com's center list.