The purpose of this study was to provide content validation for quality indicators included in an observation instrument developed to evaluate classrooms serving students with autism spectrum disorders (ASD). A panel of 103 subject-matter experts consisting of a mixture of field personnel (n = 64; 59 classroom teachers, five school administrators) and university faculty (n = 39) provided feedback regarding construct validity. Results were analyzed using two approaches: a simple aggregation of responses in the form of averages, with an a priori threshold for the determination of what will be considered acceptable, and Lawshe's Content Validity Ratio methodology. All items in the instrument were deemed to have demonstrated content validity as did the overall instrument. Based on the data from this study, the Quality Indicators for Classrooms Serving Students With ASD (QIASD) instrument can be considered to have demonstrated content validity.