Context: Public health leaders recommend systematically screening patients for social determinants of health (‘social risks’) and referring those with risks to social services, but little research has assessed how to support implementation of such activities, especially in primary care clinics serving socioeconomically vulnerable populations. Objective: To test the effectiveness of a 6-month technical support intervention at helping community health centers (CHCs) adopt social risk screening and referral activities. Study Design: Stepped-wedge trial, with 30 clinics (5 clinics per wedge x 6 wedges) receiving the intervention, in September 2018-July 2021; mixed-methods data collection within a realist evaluation framework. Setting: The CHCs are members of OCHIN, Inc., through which they share an electronic health record (EHR); they are located in 8 states. Intervention: An implementation support team (practice coach, EHR trainer, and social risk expert) guides study clinics through a 5-step implementation process over a 6-month period providing materials and support for each step. This support is adapted as feasible to meet individual clinics’ needs, and / or to improve the support provided based on ongoing learnings. Outcomes: Adaptations made to how / what implementation support was provided; change in rates of social risk screening and referral-making, pre- vs. post-intervention. Results: Adaptations to the implementation support included revising: the approaches used to identify clinic needs and goals; the workflow planning tool; the timing of when clinics were trained in using relevant EHR tools; the ratio of one-on-one to peer learning calls; the extent to which clinics were expected to report on their progress; the timing of seeking study clinic feedback; setting expectations for activities conducted between calls; the ratio of support from staff in different roles (EHR trainer : practice coach); and how implementation support was provided to clinics that had past experience conducting social risk activities. Outcomes to be reported: We will provide descriptive statistics from participating clinics to date (wedges 1-4), including change in rates of social risk screening and referral-making; we will also present lessons learned on how to implement SDH-related activities in the primary care setting, with pragmatic tips for those seeking to start or improve such activities.