Emerging social writing platforms offer possibilities for language learners to collaborate around joint assignments. One such environment is the wiki, generally hosting two prominent modes of usage, web pages and discussion forums. This study investigates software engineering students' use of a wiki as an integrated tool within the frames of a language course. The purpose of the case study was to investigate the student interaction in a student driven design setting and what the implications are for language learning in such an environment. The findings show that the two modes of interaction host primarily three types of activity, contributing and writing together, evaluating and peer reviewing, and arguing and discussing. These three activities convey different ways of collaborating and sharing text online. Once a group had chosen a mode for their collaboration, they tend to stay with it throughout their work.