Both scripted lessons and unscripted task analyzed lessons have been used effectively to teach science content to students with intellectual disability and autism spectrum disorder. This study evaluated the efficacy, efficiency, and teacher preference of scripted and unscripted task analyzed lesson plans from an elementary science curriculum designed for students with intellectual disability and autism spectrum disorder by evaluating both lesson formats for (a) student outcomes on a science comprehension assessment, (b) sessions to criterion, and (c) average duration of lessons. Findings propose both lesson types were equally effective, but unscripted task analyzed versions may be more efficient and were preferred by teachers to scripted lessons. Implications, limitations, and suggestions for future research are also discussed.