The purpose of this study was to test the reliability and validity of the Inclusive Classroom Profile (ICP), an observation measure designed to assess the quality of classroom practices in inclusive preschool programs. The measure was field tested in 51 inclusive classrooms. Results confirmed and extended previous research findings, providing further evidence for the measure's interrater reliability, factor structure, and construct validity. New information from testing the relationship between the ICP and key program characteristics provided support for the measure's discriminant validity. Reports on the ease of use of the ICP from state assessors involved in collecting data for the study indicate that the ICP holds promise for use in quality assessment. Findings from the present study are discussed with respect to implications for use of the ICP in research, policy, program evaluation, and professional development.