Can online collaboration yield a positive effect on academic writing in a foreign language? If so, what exactly is the added value, compared to individual writing, and (how) does it translate to better output? These are the central questions addressed in this paper. L2 writing research has long highlighted the benefits of collaboration in terms of both L2 learning and text quality. Most recently, the positive effect of co-ownership and peer feedback on process and product has been emphasized in studies on Computer-Supported Collaborative Writing. What has remained underexplored is the impact of web 2.0 technologies on "advanced" L2 writing. The present paper bridges this gap through an empirical study combining Web 2.0 technologies with an academic writing task. Collaborative and individual writing processes and products are compared by applying a mixed-methods approach. The results shed new light on claims made in previous studies that collaboration leads to higher text accuracy. No statistically relevant difference was found between the individual and collaborative syntheses in terms of complexity, accuracy, and fluency. However, collaborative texts score significantly higher on appropriate content selection and organization. Analysis of the process data shows that this is due to in-depth discussions during the planning phase.