This study will iteratively develop and test an adapted professional development (PD) model to be used with the Advancing Social-communication And Play intervention. Special education research suggests that current PD models may not sufficiently improve educator practice and student outcomes, or lead to sustained implementation. We propose that iteratively developing a PD model grounded in Normalization Process Theory (an implementation science approach in complex health interventions) will result in a PD model that is more feasible for preschool educational teams and more effective in changing educator practices and student outcomes. The study will include three phases: (1) feedback and adaptations, (2) design experimentation, and (3) a pilot efficacy study.