Course-based undergraduate research experiences (CUREs) enhance student retention in STEM, particularly among students who belong to historically excluded communities. Yet the mechanisms by which CUREs contribute to student persistence in STEM remain poorly understood. Our study explored how enrollment in the Tiny Earth CURE – which focuses on students discovering antibiotics from soil bacteria – promotes scientific self-efficacy and identity, while mitigating losses in STEM persistence intentions that are typical in gateway courses. The session will share results from the study and an overview of the Tiny Earth curriculum.