| The substantial health and societal effects of substance use disorders (SUDs)–and opioid use disorders (OUDs) in particular–emphasize the need for empirically supported treatments. There remains an increasingly relevant need for large-scale dissemination, implementation, and sustainment of these evidence-based treatments and practices (EBT/Ps), such as MedicationAssisted Treatment (MAT) and Motivational Interviewing (MI), to effectively reach those impacted by OUDs. The Community-Based Learning Collaborative (CBLC) is a model designed to implement EBPs across levels of systems within communities and aims to sustain these practices following implementation. Extant CBLC literature evaluated two implementation projects highlighting promising results regarding CBLC effectiveness targeting EBTs for adults with OUD and related SUD problems, and the sustainment of CBLC-related improvements targeting child post-traumatic stress and related EBT/Ps. No studies to date have evaluated the sustainment of CBLC-related improvements in the dissemination and implementation of EBT/Ps for SUD and OUDs. The current study evaluated archival and novel data from participants involved in a CBLC focused on OUD and related MAT and MI dissemination and implementation in southeast Idaho. Data came from 19 behavioral and prescribing clinicians and case brokers who participated in one of IRIHC’s four year-long CBLC cohorts and completed related surveys, pre-CBLC, post-CBLC, and at 1–2 years follow-up. Consistent with prior IRIHC findings and study hypotheses, results generally indicated significant, medium-to-large pre- to post-CBLC increases in participants’ SUD, OUD, MAT, and MI related competencies and adherence to MI-indicated practices (gs = 0.41, 0.64, 0.85, 0.99, and 1.08). As also predicted, but more novel, results indicated that CBLC-related improvements were significantly sustained 1–2 years after CBLC participation, with some implementation targets continuing to significantly improve. Findings also highlighted the potential effects of CBLC dosage in terms of different implementation curricula and/or discrepant outcomes for implementation versus deimplementation of MI-indicated and -contraindicated practices. Collectively, these findings are the first to support the CBLC’s effectiveness at sustainably improving MI- and MAT-related fidelity at 1–2-year follow up, further validating the CBLC’s scale-out utility and generalizability across different service sectors, communities, client populations, and EBTs. Keywords: evidence-based treatments, dissemination, implementation, sustainment, opioid use disorder, community-based learning collaborative |