Horner et al. (2005) present a review substantiating how single-subject research methodology can be utilized to determine whether interventions are evidence-based practices (EBPs). The current study utilized the Horner et al. research piece to: (a) systematically identify a set of quality standards for the evaluation of single-case research methodology used with learners with autism spectrum disorders (ASD), (b) operationalize these standards for evaluators, (c) investigate three additional quality indicators related to external validity (multiple studies, locations, and researchers), (d) create a protocol for evaluators, and (e) gather and analyze data from studies that meet a set of predefined criteria. Published in seven journals across ten years, identified studies (N = 160) were subjected to an analysis across 23 EBP quality standards that revealed increasing compliance with EBP standards over time yet persistent and pervasive difficulty in adequately satisfying at least five indicators integrally tied to external validity. (Contains 5 tables and 5 figures.)