The advancing social-communication and play (ASAP) intervention was designed as a classroom-based intervention, in which the educational teams serving preschool-aged children with autism spectrum disorder are trained to implement the intervention in order to improve these children's social-communication and play skills. In this 4-year, multi-site efficacy trial, classrooms were randomly assigned to ASAP or a business-as-usual control condition. A total of 78 classrooms, including 161 children, enrolled in this study. No significant group differences were found for the primary outcomes of children's social-communication and play. However, children in the ASAP group showed increased classroom engagement. Additionally, participation in ASAP seemed to have a protective effect for one indicator of teacher burnout. Implications for future research are discussed.