This study investigates the role of peer interaction (PI) and peer corrective feedback (PCF) in developing EFL learners' grammatical competence regarding simple past tense. It is based on training university-level English preparatory class students in Turkey to interact with their peers and give oral corrective feedback to each other's target grammar errors during communicative tasks. Three classes (n=85) were randomly assigned to the peer interaction (PI) group, the peer interaction and recast (PI+Recast) group or the peer interaction and metalinguistic feedback (PI+MF) group. The PI group was only trained to do communicative tasks in pairs and did not receive any feedback training; however, the PI+Recast group and the PI+MF group were trained to give recasts and MF, respectively. Pairs of learners were audio-recorded while they were trying to complete communicative activities that required the use of the simple past tense. 21 hours of audio-recorded data obtained from the learners' dialogues were examined for instances of PCF. Furthermore, receptive and productive measures were used to identify the effects of the intervention. The findings show that the PI+Recast and PI+MF groups performed better than the PI only group in terms of receptive knowledge and accurate use of the simple past tense.