ABSTRACT Asthma is the most common chronic disease of childhood and causes more preventable hospitalizations and lost school days than any other childhood disease. Children in lower-income, urban, and racial/ethnic minority populations are more likely to have asthma, to have poorly controlled disease, and to experience preventable morbidity. Multi-level interventions that address the complex array of interrelated societal and environmental factors that contribute to these disparities are poorly supported in traditional fee-for-service payment models. In contrast, accountable care organizations (ACOs) are designed to support and sustain interventions that address social determinants of health as part of medical care. A substantial and growing number children with asthma in higher-risk populations receive care in ACOs, but their effect on asthma quality of care, outcomes and disparities is not known. This study will be the first to address this critical gap in knowledge by taking advantage of a natural experiment taking place in Massachusetts (MA), a state with high rates of childhood asthma: In 2018, MA, launched 17 new Medicaid ACOs with varied organizational features (e.g., size; age mix). We will use detailed state-level claims data to: 1) determine the association between implementation of the ACOs and changes in childhood asthma quality indicators, health outcome for Medicaid-insured children and 2) assess changes in socioeconomic and racial/ethnic disparities in these outcome measures comparing children enrolled in Medicaid ACOs to matched commercially-insured children. We then turn to understanding the influence of ACOs’ organizational features on change by: 3) using mixed-methods to generate detailed characterizations of the ACOs’ organizational features and 4) test the association between these features and childhood asthma quality indicators and outcomes. We will use innovative methods of risk adjustment that take social risk factors into account and propensity matched difference- in-difference analyses to account for factors other than ACO implementation that may affect outcomes. This study will take place at a moment when the profound inequities in health and healthcare in the U.S. are starkly illuminated by the COVID-19 pandemic. Socioeconomic and racial/ethnic disparities in childhood asthma persist despite the existence of evidence-based treatments resulting from decades of work and billions of dollars directed at improving asthma care. Structural changes in healthcare are needed for equitable delivery of evidence-based asthma care, which should reduce or even eliminate these long standing disparities. The ACO model moves healthcare payment and delivery in a direction that could facilitate this change. This study will address major gaps in knowledge as to whether the large investments being made in developing the ACO model may pay off for the millions of children at increased risk for long-term poor health due to preventable cons...