Writing is, to a considerable degree, a social process in which writers talk within themselves or with readers. Collaborative learning specifies the social dimension of writing by providing a knowledge community in which students learn to write through interacting with a capable peer. In writing groups, students develop concepts of audience and receive emotional support from encouraging peers. Integrating collaborative pedagogy into the regular course syllabus increases the effectiveness of writing instruction. This paper explores the social dimension of writing through reviewing related literature and investigating students' behavior in the classroom. Students' comments about peer review are provided to show the efficacy of collaborative learning strategies in an EFL writing class.