While there is growing recognition and acceptance of Open Educational Resources (OER) and Open Educational Practices (OEP) in teaching and learning, designing for their integration remains very challenging for educators. Adopting OER and OEP in their profession requires significant changes in practitioners' pedagogical thinking and practices, which can be supported by the design of appropriate professional development experiences. At the Open University of Sri Lanka (OUSL), significant successes in addressing this challenge have been achieved with the design and development of a rigorous approach and a robust model to support adoption of OER and OEP by practitioners using Scenario-based Learning (SBL). In this paper we explore the efficacy of a scenario-based approach to learning in the integration of OER by practitioners, reflecting on how the SBL approach was tested and refined over three continuing professional development (CPD) interventions conducted at the OUSL over 2013-2017. Based on the findings, we discuss what design strategies of the three CPD interventions best supported the adoption of OER and OEP by practitioners, how effective have been the theoretical constructs and the strategies adopted in the design of CPD interventions, the impacts of the CPD interventions and implications of these experiences for the future.