School participation and connectedness have significant implications for student outcomes while at school and in later life. The need to develop evidence-based interventions to proactively support students with autism spectrum disorder (ASD) is imperative. A two-round Delphi technique was used to gain expert consensus to inform the development of a school-based intervention to improve the school participation and connectedness of elementary students with ASD. Seventy-six expert clinicians, educators, and researchers completed Round 1 and 65 completed Round 2. Consensus was achieved on the application of a conceptual framework of participation in Round 1, which informed the theoretical rationale of the intervention. Consensus on the importance of proposed classroom modules and the feasibility of proposed intervention techniques was achieved in Round 2. The process of gaining expert perspectives to develop an evidence-based intervention provides greater confidence that the intervention will be effective in achieving meaningful outcomes for students with ASD.