ICH was the evaluator for SUSTAIN Communities, an initiative funded by the GE Foundation with support from Partners HealthCare. SUSTAIN Communities provided grants and technical assistance to community health centers to build capacity for office-based addiction treatment and provision of medication for opioid use disorder (MOUD). The program was run by the Massachusetts League of Community Health Centers and included three cohorts of community health center grantees, with a total of 26 grants to 17 health centers. ICH designed and implemented a mixed-methods evaluation of each cohort to assess the impact of the program on staff and organizational capacity to provide MOUD services. The cohort-specific evaluations utilized a range of data collection approaches, including staff surveys, capacity assessments, staff and patient interviews, focus groups, and grantee progress reports. In addition, ICH conducted a cross-cohort quantitative analysis to examine how program dosage affected capacity growth outcomes and to examine associations between capacity growth and the volume of patients receiving MOUD. Data collected through the evaluation helped individual health centers identify gaps and areas of focus to optimize their programs, and helped the grant managers and funder identify the areas of highest need for training and technical assistance offerings in the future. The cross-cohort evaluation findings provided evidence to support the hypothesis that participation in SUSTAIN improved health centers’ knowledge and skills around care for patients with opioid use disorder, and that this was linked with growth in MOUD patient panel sizes.