The grizzled Callaway has spent the past three seasons in his position at Western Kentucky. He was UAB’s coach from 2007–11, compiling an 18–42 record.
Before that, the 60-year-old Callaway was Georgia’s offensive coordinator and offensive line coach for six seasons following four years in the same positions at his alma mater, Alabama. He was Houston’s associate head coach and offensive coordinator from 1993–96 under Helton’s father, Kim.
Callaway joins Helton, who was promoted to permanent head coach late last month after being made the Trojans' interim coach in October when former Trojans coach Steve Sarkisian was fired. Helton began the season as USC's offensive coordinator and quarterbacks coach. The Trojans won the Pac-12 South this season and finished with an 8–6 record, which included a 5–4 mark under Helton.