Effective data collection requires routine assessment of interobserver agreement (IOA). This study evaluated a supervisory intervention to increase the frequency of IOA assessments performed by educational staff at a school for children with developmental disabilities. Intervention components included action directives, strategic posting of IOA recording forms, and performance feedback (positive reinforcement and correction). Implemented in a multiple baseline design, intervention increased IOA assessments targeting skill acquisition and behavior support plans. The study illustrates a systems-level approach towards performance enhancement of human services personnel.