This study focuses on the use of wikis in collaborative writing projects in foreign language learning classrooms. A total of 34 intermediate level university students learning English as a foreign language (EFL) were asked to accomplish three different wiki-based collaborative writing tasks, (argumentative, informative and decision-making) working in groups of four. Student wiki pages were then analyzed to investigate the role of task type in the number of self and peer-corrections as well as form-related and meaning-related changes. In addition, focus-group interviews and questionnaires were conducted to find out how students would describe their overall experience with the integration of a wiki-based collaborative writing project in their foreign language learning process. The results revealed that the argumentative task promoted more peer-corrections than the informative and decision-making tasks. In addition, the informative task yielded more self-corrections than the argumentative and decision-making tasks. Furthermore, the use of wiki-based collaborative writing tasks led to the accurate use of grammatical structures 94% of the time. The results of the study also suggest that students paid more attention to meaning rather than form regardless of the task type. Finally, students had positive experiences using wikis in foreign language writing, and they believed that their writing performance had improved.