This study investigated the impact of Open Educational Resources (OER) on the professional development of Bhutanese Physics teachers. Collaborating with partner institutions in Tanzania, Nigeria and India, Samtse College of Education developed and implemented three physics modules: Force and Motion; Work, Power and Energy; and Electromagnetism. These OER incorporate activity-based learning, technology integration, Universal Design for Learning (UDL) and design thinking principles. A mixed-methods approach, including pre-test and post-test scores, lesson plans, reflections, and interviews were used to assess the impact of OER on teacher's Subject Matter Knowledge (SMK), Pedagogical Content Knowledge (PCK) and General Pedagogy Knowledge (GPK). Additionally, the study examined a Community of Practice (CoP) on Telegram to understand knowledge sharing within the community. The findings revealed that most teachers demonstrated improved proficiency level after using OER, thus positively impacting their professional development by enhancing content knowledge, technological skills, and pedagogical practices. However, some teachers require further enhancement in SMK and PCK especially in Work, Energy and Power and Electromagnetism modules. The use of CoP proved valuable for knowledge sharing and collaboration. The study recommends educational institutions support the Continuous Professional Development (CPD) of Physics teachers by providing access to OER for their use and additional resources to enhance their SMK and PCK.