Homeless Veterans with substance use disorders (SUDs) are a major group served by VA and are heavily represented in VA housing. VA recently adopted a 'Housing First' approach emphasizing rapid housing placement to initiate recovery without requiring sobriety and will necessitate SUD interventions that are efficient and easily layered onto existing services. The proposed study will investigate the effectiveness, implementation process, and cost estimate of Group Motivational Interviewing (GMI) for Veterans with SUDs in VA housing (Housing Urban Development-VA Support Housing [HUD-VASH] and Grant and per Diem [GPD]). Outcomes will be assessed at multiple time points using a multi-modal approach. The ultimate goal of this research is to establish the basis of a GMI dissemination and implementation course of action for highly vulnerable homeless Veterans in VA housing for achieving their greatest success in attaining housing stability.