This study contributes to scant empirical investigation of peer critique of writing among heterogeneously grouped native and nonnative speakers of English, now commonplace in higher education. This mixed-methods study investigated the use of directed peer review to improve writing among graduate students, the majority of whom were nonnative speakers of English. Following a modified version of the "Optimal Model" of peer critique of university coursework, statistically significant gains were realized between the initial draft of a business proposal and its final submission for each of the measured items: support, audience focus, writing conventions, and organization. In addition, during the qualitative phase, students were observed to identify how peer editors naturally engaged in probing and collaborative styles of feedback known as "discovery mode" interactions. Approximately 80% of the students engaged in interactions to clarify the text and align it with the author's intentions, and approximately 37% sought to enhance and develop the text. Finally, the results suggest that the face-to-face peer review did improve the quality of a business communication assignment and implies a number of essential instructional practices toward improved writing and collaboration. (Contains 3 tables.)