Online learning has matured as a mechanism that can change how we deliver education. Open education resources are proliferating, and institutions are creating massive open online courses (MOOCs). In addition, efforts are underway to develop platforms that allow individuals to create, lead, and participate in their own courses. This bottom-up, peer-to-peer model of education illuminates new dilemmas. For example, open learning environments are heavily dependent on voluntary individual participation, but such participation is difficult to foster. In this paper, we use log data from the Peer 2 Peer University (P2PU) to explore factors related to active participation in a series of teacher, professional development courses (the P2PU School of Education). We employ learning analytics to identify how features such as course page design and course organizer activity interact with new and returning participants to foster increased participation in open learning groups.