The K-12 Student Success: Out-of-School Time Initiative is focused on boosting student success among Oregon's middle school students. Thus far, The Oregon Community Foundation and The Ford Family Foundation have funded 47 organizations that provide out-of-school time (OST) programming (e.g., after school or summer) to rural students, students of color and low-income students. Funded programs emphasize academic support, positive adult role models and family engagement, and are participating in an ongoing learning community to support program quality through the Initiative. This learning brief summarizes what is known about social and emotional learning (SEL) from existing research, and shares what we are learning about the efforts of grantee organizations to promote social and emotional skill development among the youth who participate in their programming. We hope that this brief builds greater understanding of the practices and experiences of OST programs in Oregon.