Peer collaborative second language (L2) writing has recently gained a lot of traction (Hu & Lam, 2009; Swain & Lapkin, 2013) as both instructors and students recognize its advantages. Although research on peer feedback in L2 contexts has a long history, peer collaborative L2 writing research has been sparse. This article reports on a study that investigated student perceptions on collaboration in an extended, take-home writing assignment in an English for academic purposes context at a Canadian university. Data were collected from questionnaire surveys, student writing, and semistructured interviews. Findings suggest that although there are some challenges in peer collaborative writing, it also has certain benefits. The main challenges identified were participants' unfamiliarity with peer collaboration, lack of clear instructions regarding the steps to be followed, unequal proficiency levels within groups, and group members' different backgrounds, causing difficulty in communication among partners. The benefits include students' critical awareness about the use of language in academic writing, which led to an improved understanding of the meaning-making processes in text production. Drawing on these findings, the authors discuss implications for teaching and learning.