Wikis constitute one of the most promising Web 2.0 technologies. However, there seems to be a knowledge gap in the literature concerning their effective integration in undergraduate education. Previous research indicated that student participation in wikis is minimal and that on-line collaboration and interaction are particularly limited. This paper presents data from a longitudinal research project which aims at the progressive refinement of a wiki task using a design experiment method. The effect of a third version of a wiki task on student participation, online collaboration and interaction was examined in an undergraduate course with 56 participants. The results indicated that, while student participation rates and online interactions were substantially improved compared to an earlier version of the task, student online collaboration remained minimal.