This systematic review examined definitions of “nonverbal” or “minimally verbal” and assessment measures used to evaluate communication in intervention studies focusing on improving expressive verbal communication in children with autism spectrum disorder (ASD). We reviewed sample size, number of participants, participant age, and male/female representation. Our analysis yielded relatively few studies with non/minimally verbal children with ASD focusing on verbal expressive communication. Further, we found large inconsistencies in measures used, definitions of “nonverbal” and “minimally verbal”, and ages targeted. Guidelines are suggested to create a more uniform assessment protocol with systematic descriptions of early communication learners as a foundational step for understanding the heterogeneity in this group and replicating research findings for this subgroup of children with ASD.