The aim of this study was to examine the effects of an instructional adaptation (reduction of task duration) on off-task behavior in a general education classroom. The intervention was chosen following a functional behavioral assessment, which suggested that much of the off-task behavior was escape-maintained, and a curriculum-based assessment, which showed an appropriate curriculum/performance match. An alternating-treatments design was used to assess the impact of the intervention. Results revealed that the reduction of task duration was effective in decreasing the level of escape-maintained off-task behavior during independent work in mathematics. Attention-maintained off-task behavior was not affected. Implications of these findings for both assessment and intervention planning are discussed.