In this systematic evaluation of intervention research for transition-age autistic youth, we examined quality indicators in 193 group and single-case design intervention studies, which tested effects on 1258 outcomes. Behaviorally based interventions were the most common intervention type. We found significant threats to internal validity for the majority of studies, including inadequate randomization, unmasked assessors, and too few data points to infer functional relations. The majority of outcomes were measured in contexts similar to the intervention and were conceptualized as behaviors directly addressed by intervention procedures. As such, they are of unclear long-term utility for autistic people entering adulthood. Adverse events were rarely reported. We suggest several avenues for improving intervention research for this age group.