Many prompting procedures exist for teaching skills to individuals with autism spectrum disorder and intellectual disability; however, direct comparisons between variations of prompt delay are rarely made. Here, we compared three variations of prompt delay (2-s or 5-s constant delay and 5-s progressive delay) alongside trial-and-error instruction. Four learners were taught a conditional discrimination task using a match-to-sample arrangement. Performances were compared using effectiveness and efficiency measures in an adapted alternating treatments design. A procedural modification, in the form of differential reinforcement, was applied to the prompt delay procedure for two of the four participants. With or without this procedural modification, results suggest progressive prompt delay may be effective and the most efficient in reducing learner errors during instruction.