Despite recent advances, the evidence base supporting early intervention for young children with autism spectrum disorder (ASD) remains relatively sparse. The International Society for Autism Research (INSAR) recently sponsored a Special Interest Group (SIG) on Implementing and Evaluating Community-Based Early Intervention. Across three meetings, in 2015, 2016, and 2017, conveners of this SIG engaged >200 members to identify knowledge gaps and research priorities for moving the field forward. Here, we summarize the perspectives that emerged from group discussion at the SIG meetings as represented by scholars working actively in the field. Despite encouraging progress, critical gaps and research priorities were identified across all the stages of intervention development and testing from conceptualization to community implementation. Key issues include the need for (a) formal theories to guide early intervention development, evaluation, and implementation; and alignment of intervention goals with scientific knowledge and societal changes that have occurred in the decades since interventions were originally developed; (b) increased focus on feasibility of treatment procedures and alignment with stakeholder values during pilot evaluations; (c) use of research designs that allow for comparisons of different interventions and formats, analyses of active ingredients of treatment, and identification of moderators and mediators of outcome; (d) use of community-partnered participatory research to guide adaptation of intervention models to community settings; (e) inclusion of constructs related to implementation processes and outcomes in treatment trials and; (f) an iterative approach to the progression of knowledge from intervention development to implementation. Autism Res 2018, 11: 16-23. Lay Summary: In this article, we summarize the themes discussed at the INSAR Special Interest Group (SIG) on Implementing and Evaluating Community-Based Early Intervention. Priorities for moving the field forward identified in the SIG included the need for (a) formal theories to guide the development and evaluation of interventions, (b) pilot evaluations that investigate feasibility and acceptability of interventions, (c) methodologies that allow us to determine for whom different interventions bring most benefit and why this is so, (d) strategies to include community members and other stakeholders in the process of developing and evaluating interventions, and (e) understanding of factors that make interventions more likely to be adopted and successfully implemented in the real world.