The authors of the current investigation developed and evaluated the effects of a tutoring system based on a small-group arrangement to two young adults with autism spectrum disorder on the acquisition, maintenance, and generalization of sight words. The tutoring system was comprised of a virtual teacher to instruct sight words, and a humanoid robot which adopted a peer metaphor, where its function was to act as an emulated peer. With the introduction of the robot peer (RP), the traditional dyadic interaction in tutoring systems was augmented to a novel triadic interaction in order to enrich the social content of the learning environment and to facilitate observational learning (OL). The virtual teacher implemented a constant time delay strategy to instruct three types of sight words: (a) target words exclusive to the participant, (b) target words common between the participant and the RP, and (c) nontarget words exclusive to the RP. In order to examine the efficacy of intervention, a multiple-probe design across three word sets, replicated across two participants, was utilized. Results indicated that both participants acquired, generalized, and maintained target words with 100% accuracy. Furthermore, the participants made fewer errors and required less instruction time to learn the words common between the participants and the RP. Finally, the participants acquired, through OL, the majority of words taught exclusively to the RP.