The purpose of the present study was to investigate the effectiveness of an IBR intervention and a PA intervention on the vocabulary and emergent literacy of preschool children with ASD. Based on a series of three planned consecutive randomized controlled trials (RCTs), the following research questions were addressed: Research Question 1: Do preschool children with ASD exhibit significant growth on vocabulary and emergent literacy over the course of their prekindergarten year, regardless of what experimental condition they experience? Research Question 2: What are the effects of IBR and PA interventions on vocabulary and emergent literacy for preschoolers with ASD? Research Question 3: Are the effects of IBR and PA interventions on vocabulary and emergent literacy growth accounted for by observed time spent on related classroom literacy activities? (author abstract)