Opioid Use Disorder (OUD) is a national health crisis. Office-Based Opioid Treatment (OBOT) with buprenorphine/naloxone (B/N) prevents overdose deaths. Psychosocial stress and psychiatric problems (e.g., Anxiety) are major reasons for OBOT drop out and relapse. Many patients turn to benzodiazepines (BZD) to address anxiety and emotional distress with dangerous consequences, non- pharmacologic approaches to anxiety, stress, and emotion dysregulation are needed during primary care OBOT, which is the primary access point for OUD treatment in most US counties. Mindfulness- Based Interventions (MBI) safely and reliably reduce the impact of stress, anxiety, depression, and chronic pain, which could increase OBOT retention, while reducing rates of relapse and overdose deaths. However, current 8-week standard MBIs do not appear to have strong, sustained impact on substance use outcomes, suggesting longer or enhanced MBIs are needed in the OUD treatment setting. This project proposes to adapt, refine and compare the effectiveness of the 6-month Mindful Recovery OUD Care Continuum (M-ROCC) delivered within Group-Based Opioid Treatment (GBOT) versus standard GBOT alone. M-ROCC is derived a three phase program derived from the evidence-based, established Mindfulness Training for Primary Care (MTPC) program, which has been adapted for Opioid Use Disorder. M-ROCC includes a flexible, patient-centered, motivationally responsive design, including a 4-week Low Dose Mindfulness Entry Group, Mindfulness Maintenance Check-in Support Group, and an 8-week intensive Mindfulness Training for Primary Care (MTPC-OUD) Group. M-ROCC builds on the previously demonstrated ascending mindfulness practice dose ladder approach, which helps individuals with OUD nurture motivation and resolve ambivalence for mindfulness practice. MTPC has been shown of lower anxiety, stress, and depression, while increasing self-efficacy and capacity for behavioral change by engaging self-regulation mechanisms. During the R21 phase, we will prepare for a multi-site RCT by 1) adapting the M-ROCC manual; 2) training providers at 5 MA primary care sites to lead M-ROCC; 3) piloting M-ROCC assessing qualitative feedback for iterative refinement; 4) manualizing GBOT and offering training to MA OBOT sites; and 5) preparing for the R33 phase by obtaining necessary approvals and site contracts. In the R33 phase, we will conduct a five-site RCT comparing M-ROCC plus GBOT with GBOT alone for 200 primary care patients prescribed B/N for OUD, primarily evaluating its impact on opioid use and anxiety, but also on cocaine and BZD use, as well as aspects of self-regulation needed for sustained addiction recovery.