This quasi-experimental study is aimed at (a) teaching learners how to provide corrective feedback (CF) during peer interaction and (b) assessing the effects of peer interaction and CF on second language (L2) development. Four university-level English classes in Japan participated (N= 167), each assigned to one of four treatment conditions. Of the two CF groups, one was taught to provide prompts and the other to provide recasts. A third group participated in only peer-interaction activities, and a fourth served as the control group. After one semester of intervention, the two CF groups improved in both overall accuracy and fluency, measured as unpruned and pruned speech rates, whereas the peer-interaction-only group outperformed the control group only on fluency measures. This study draws on monitoring in speech-production theory and the declarative-procedural model of skill-acquisition theory to interpret these results, thus contributing a new theoretical approach to CF research in the context of peer interaction in which learners can be providers of CF. It is concluded that whereas peer interaction offered opportunities for repeated production practice, facilitating proceduralization, CF sharpened learners’ ability to monitor both their own language production and that of their interlocutors.