Health disparities in ASD detection affect children's access to subsequent interventions. We examined potential disparities in implementation of a multi-stage ASD screening and diagnostic evaluation protocol in Part C Early Intervention with 4943 children ages 14-36 months (mean 22.0 months; 62.9% boys, 73.3% children of color, 34.9% non-English-primary language, 64.5% publicly-insured). Participation and follow-through were high (64.9% and 65.3% at first- and second-stage screening, respectively, 84.6% at diagnostic evaluation). Logistic regressions identified predictors of screening participation and outcomes at each stage; demographic differences (race, language, public insurance) were observed only at first-stage screening and reflected higher participation for children of color and higher positive screens for publicly-insured children. Results suggest the multi-stage screening protocol shows promise in addressing disparities in early diagnosis.