Peer feedback plays a pivotal role in stimulating students' participation in L2 writing, which has the potential to develop students' writing skills. The concept of metacognition has also been examined to facilitate learner writers in their learning process. As such, this study drawing upon the concept of metacognition explores the implementation of peer feedback in English as a foreign language (EFL) tertiary writing classes in Vietnam and based on the findings develops a peer feedback approach to enhance the learners' metacognition. Data were collected from semi-structured interviews with sixteen English majors and classroom observations in two English writing classes at a university in Vietnam. Content analysis of the data revealed that peer feedback was informally implemented in two EFL writing classes under study, which might suggest that few opportunities for the students to develop their metacognition could be provided in this current feedback approach. The findings also demonstrated the learners' expectations for changes in peer feedback practice in their writing classes. Thus, the study suggested a jigsaw peer feedback approach which met the participants' desires and simultaneously afforded the learners a number of opportunities to improve their metacognition in EFL writing contexts, especially in Vietnam. This study helps to extend the literature in peer feedback approach in L2 writing which is underpinned by the concept of metacognition and offers both pedagogical and theoretical implications in English language teaching (ELT).