This study examines what role English writing instructors need to play in peer revision activities. Students participating in the study were asked to go through multiple draft writing process in which they wrote three drafts on each writing assignment and review their peers’ essays in both a written comment sheet and an oral discussion. Overall, the results show that the peer comments played little role in improving the students’ essays from the first to second drafts. However, great improvement is observed from the second to final drafts. Specifically, little effect of the feedback on the improvement of non-linguistic features of the essays is identified. Regarding the linguistic features, improvement was made from the second to final drafts. However, it is achieved by both the peer and teacher comments. Therefore, it is concluded in the study that the teacher comments played a role in helping the students produce the linguistically improved final drafts. The study recommends the instructor’s explicit, detailed feedback to the errors caused from students’ insufficient writing and English competence.