ABSTRACT Despite the widespread availability of low-cost, evidence-based preventative strategies like human milk feeding, feeding guidelines and medication stewardship, necrotizing enterocolitis (NEC) remains a chief cause of emergency surgery and death in premature infants and disproportionately affects Black and Hispanic infants. Under-resourced neonatal intensive care units (NICUs) struggle to support staff education, a culture that engages in quality improvement (QI), or access essential resources like donor human milk and adequate nursing care. The intersectionality of these factors in concert with social determinants of health may contribute to NEC disparities. NICU disparities are lessened with intense quality improvement, although equity-focused quality improvement is rare. In 2016, the U.S. Legislature signed the “Expanding Capacity for Health Outcomes (ECHO) Act” into law to spur “technology-enabled collaborative learning and capacity building models” and accelerate the impact of these models on preventing disease and improving public health outcomes among underserved groups. Our team has effectively implemented a neonatal Project ECHO (NeoECHO) which supports implementation of NEC preventing best practices and our team has shown its benefits to reach NICU clinicians in under-resourced settings. Using a stepped-wedge clinical trial design and engagement of patient- family advocate partners and a national neonatal practice group, we will provide active facilitation via tele- mentoring and working with local internal facilitators in 30 NICUs to examine the effects of a NeoECHO approach to reduce NEC rates and impacts on NEC disparities within and across units. Aims will: 1) Compare the effectiveness of NeoECHO to usual care on NICU-level outcomes for NEC and clinical care. 2) Describe the structural organizational contexts and unit-level differences in quality outcomes at baseline and examine their contribution to intervention effectiveness. 3) Evaluate NeoECHO implementation (including features of engagement, reach, number of recommended practices adopted and embedded in practice, retention of NICUs in the program, effect on clinician confidence, and cost). Using an implementation determinant framework known as the Health Equity Implementation Framework, we will qualitatively explore the barriers and facilitators to implementation of NeoECHO to allow for a more contextual understanding of implementation disparities. Our pragmatic, experimental design will expand the evidence base on both effectiveness and implementation of ECHO and contribute to the AHRQ mission by addressing modifiable risk factors to reduce disparities in the incidence of NEC; leveraging telehealth-delivered mentoring to facilitate adoption of EBP by removing accessibility barriers; and offering at-the-shoulder support for NICUs most in need. This application is responsive to the AHRQ Special Emphasis to Advance Health and Healthcare Equity (NOT-HS-23-013), informing t...