This study examined changes in utilization of medical staff within organizations specializing in treatment of patients with substance use disorder (SUD) at two points in time (2007 and 2010). Utilization was calculated as the number of hours paid weekly for psychiatrists, physicians, nurses, and other medical staff working as employees or on contract. Study data come from a longitudinal national sample of 274 substance use disorder treatment centers. Average utilization of medical staff by these SUD treatment organizations increased by 26% from 2007 to 2010. The results showed that growing SUD treatment centers that obtained more referrals from health care providers, used case managers to coordinate comprehensive approaches to patient care, provided medication assisted treatment (MAT), and that were connected more closely with hospitals made increased use of medical staff over the 2007–2010 period. In 2010, these organizations seem to have been moving in directions consistent with trends forecasted for the SUD treatment environment after implementation of the Affordable Care Act.