OVERALL - SUMMARY Primary care is essential to improving population health outcomes and reducing health disparities but struggles to meet the burgeoning needs in the areas of chronic illness and prevention, mental health and addiction, and social needs, and faces challenges in access, patient experience and staff shortages. Learning health systems (LHS) hold promise for transforming primary care but the feasibility and impact of the LHS is uncertain in community settings without embedded research expertise. For LHSs to make meaningful, equitable improvements in care, they must reach systems serving individuals with low income and a disproportionate burden of illness and disparities. The Washington LHS E-STAR Center will respond by building a consortium of research organizations that are leaders in LHS training and research, and diverse primary care organizations across the state, where diverse embedded LHS researchers receive training and mentorship. The E-STAR Center is 2 premier research organizations, Kaiser Permanente Washington Health Research Institute and the University of Washington and 6 primary care organizations (PCOs)—2 integrated systems and 4 Federally Qualified Health Centers (FQHCs). Our novel LHS model for primary care transformation builds on our successful CATALyST LHS K12 training program, adding 3 innovations: increased participatory research, formalized stakeholder engagement, and a health equity focus. Mentoring teams will include expertise in community-based participatory research, and health equity in addition to expertise in PCOR/CER. We enhance participatory research by including PCO leaders in training sessions and dissemination of findings, extending our learning community beyond scholars and mentors. We move from opportunistic partnerships to formal, sustainable partnerships with diverse PCOs to support embedded research. We add healthcare impact goals and metrics, including on equity, to scholars’ development plans that set and track their training and research objectives and progress. The benefits of this new model include bidirectional learning, enhanced relevance of LHS research, proactively defining the value of research and building LHS capacity in partner PCOs. The Center will (1) build new infrastructure for bidirectional research-health care partnerships, (2) train 7 early- career researchers in embedded LHS research in partnership with PCO leaders, and (3) lead embedded LHS research in participating PCOs. These activities will enable the Center to achieve its goals of producing a diverse set of independent scientists with a solid foundation in LHS research who can change the paradigm of primary care research through embedded research that rapidly develops and implements evidence; and simultaneously building LHS capacity in safety net primary care settings.