Although wikis have been widely adopted to support collaborative writing in undergraduate classrooms, educators remain concerned about the level of student participation. Using regulation theories to design interventions in the form of activities, we examined their effects on collaborative writing on wikis. Results demonstrate that with the interventions, undergraduate confidence in using writing strategies significantly increased and anxiety about writing significantly decreased. An analysis of log files saved on wikis showed that many students actively engaged in the collaborative writing process on their wikis. Suggestions are provided for instructors and educational developers.