For more than a decade, the authors have engaged in several collaborative action research projects in established communities of practice, generating new knowledge and promoting practice development in religious education (RE) in schools and higher education. Based on this, this article asks what characterised the collaborative processes, and how the projects impacted on new RE-knowledge and practices. For some participants, the dynamics of the community of practices changed the way they came to see their own RE-teaching practice and role as RE-teachers, the relationship between RE-research and their own practice and their personal theory of practice in religious education and beyond. The degree of such changes and how they can be described, is often difficult to trace over time. A critical question raised, is whether such projects could benefit from being more explicit and detailed about their aims from the start, in collaboration with the networks that initiated the projects. This would make it more realistic to document and discuss their outputs, outcomes, and impacts, and have implications for future action research.