Objectives <p>This study tested the feasibility and outcomes of an intensive summer social program (summerMAX^yc) on the social functioning, ASD-traits, and behaviors of autistic children, ages 4–6&#xa0;years (<i>N</i> = 12). </p> Methods <p>The manualized 5-week group intervention was delivered 5&#xa0;days per week, 6&#xa0;h per day to groups of 6 children each, and it included skills instruction and therapeutic activities targeting social/social-communication skills, emotion recognition, and interest expansion. summerMAX^yc utilized direct instruction, modeling, roleplay, feedback, repeated practice, and reinforcement, and parents also participated in weekly group parent training.</p> Results <p>High levels of fidelity and child and parent satisfaction, as well as no attrition or adverse events supported feasibility. Significant pretest–posttest improvements were found for the primary outcome of child social performance (rated by masked observers), and secondary outcomes of parent-rated ASD-traits, social skills, communication skills, and problem behaviors. The results from 2 main outcome measures were pooled with prior summerMAX^yc pilot study results to explore child features potentially associated with pretest–posttest change scores. Findings suggested that change scores were not related to third variables.</p> Conclusions <p>summerMAX^yc was feasible and appeared to yield child benefits. Implications and recommendations for further study are provided.</p>