The Opioid Treatment Accreditation Course (OTAC) is a mandatory accreditation requirement in New South Wales, Australia, and aims to prepare medical practitioners for the provision of safe and effective Opioid Substitution Treatment to people with opioid dependence. The course has a strong focus on safe prescribing practices and the course design includes a Professional Practice Forum that is engaging for participants and effective at imparting complex ideas and concepts that do not place additional time constraints on already time-poor health professionals. OBJECTIVE: The study aimed to use participatory action research methods to develop and evaluate an online Professional Practice Forum that is a key component of the OTAC teaching and learning experience. METHODS: Three evaluation cycles were implemented with three cohorts of participants (N=40) to inform the design and review of the updated OTAC course. Overall, the study relied on participatory action research methods to enhance a sense of online community and to revise the Professional Practice Forum component of the course. Findings from survey feedback and an examination of Web metrics were used to monitor participant learning and were subsequently subject to thematic analysis in order to identify key themes. RESULTS: The use of participatory action techniques in the redesign of the OTAC course was a successful means of engaging with participants and resulted in four revisions based on feedback from facilitators and participants. The Professional Practice Forum was rated highly and received positive feedback from both moderators and participants. CONCLUSIONS: The use of interactive forums in online learning in an educational module for adult learners can prove extremely valuable as a means for participants to share their expertise and improve their learning outcomes. In particular, the use of sticky and welcome threads were significant features that enhanced interactions between participants and facilitators and resulted in increased quantity and quality of postings. These findings can help inform future researchers on how to develop peer engagement modules that are amenable to assessment and that build an online sense of community.