Using a multiple probe design across peer buddy-target child dyads, we evaluated the effects of an intervention package (i.e., brief training, system of least prompts, visual supports) on peer buddies' use of stay-play-talk (SPT) with their classmates who were socially isolated (target children). All six peer buddies increased their use of SPT after the intervention package was introduced. Peer buddies also maintained SPT strategy use when adult supports were faded but did not generalize implementation of SPT strategies to other settings. We also examined the relation between peer buddy use of SPT and the duration of social play for target children. The social engagement of all three target children increased after intervention commenced with peer buddies. Target children increased, maintained, and generalized their duration of social play across settings. Teachers reported the SPT strategies were feasible and perceived socially significant increases in the social engagement of the target children.