There is a great need to identify instructional methods that effectively promote positive skill development in young children with developmental disabilities. This 2-year longitudinal study evaluated the practicality and effectiveness of two delivery models of providing Discrete Trial Teaching (DTT) to children with developmental disabilities within an existing public preschool program. At baseline all participants demonstrated significant developmental delay in several areas of functioning (communication, motor skills, language, social/adaptive behavior, and cognition). In year 1 of the intervention each participant received DTT in three 10-15-minute intervals each school day. In year 2 participants received DTT in one 30-45-minute interval each school day. Participants who were exposed to both delivery models acquired new skills significantly faster and learned more in year 2, suggesting greater instructional efficiency and effectiveness when DTT was provided in one longer session. The results indicated that DTT has the potential to be used practically and effectively within existing public preschool programs to positively impact the learning and development of young children with developmental disabilities. Implications and directions for future research are discussed. (Contains 5 tables.)