For language learning, online environments allowing for user generated content are becoming increasingly important since they offer possibilities for learners to elaborate on assignments and projects. This study investigates what wikis can do as a means to enhance group interaction, when students are encouraged to participate in constructing text and exchanging peer response. The research focus is on exploring what interaction unfolds in the wiki and how it promotes language learning, from a sociocultural perspective. This interaction is framed both by affordances in the wiki but also by what is expected from students as language learners in an English for Specific Purposes class environment. The analysis has a multilevel approach, focusing on patterns of interaction and the nature of feedback. The study shows that collaboration becomes specifically interesting from a language learning perspective. In the findings, on the student wiki pages there are numerous contributions relating to both local language and global content. Revising co-constructed text opens up possibilities for the students to evaluate existing contributions and it also provides opportunities for them to suggest constructive changes. In addition, with the environment being web based, we discuss certain benefits arising from the fact that it allows for user-generated content.