This study investigates the beliefs of second language learners regarding peer interaction and peer corrective feedback (CF) as well as the feasibility of a second language intervention, aimed at changing those beliefs. The classroom intervention was designed to promote collaborative learning and to train learners to provide CF to each other. Participants were university-level learners in 4 required English classes in Japan (N=167), each assigned to 1 of 4 treatment conditions. While all experimental classes were given peer interaction instruction, 2 classes were given CF training (prompts or recasts). Another class served as the control group. Questionnaires were administered before and after the intervention and selected learners (n=36) were interviewed. The quantitative (factor-analysis and matched-samples t-tests) and qualitative (grounded theory methodology) analyses revealed that, while learners held positive beliefs about peer interaction and peer CF from the onset, the intervention facilitated trust in their classmates as learning resources, and those who were given CF training displayed an increased willingness to and confidence in providing CF. Also, 2 classroom-specific variables emerged for the intervention to be effective on language development: a collaborative classroom environment and positive social relationships between learners.