Researchers have argued that, in addition to grammar, translation, and paragraphing, students' reasoning and critical thinking skills should be emphasized when teaching English as a foreign language (EFL) writing. Studies have indicated that asynchronous debate is effective and self-paced in terms of fostering students' thinking skills due to its asynchronous nature. The purpose of this study was therefore to examine whether and how asynchronous debate could help enhance EFL students' critical thinking skills in two EFL courses. The students in both classes took turns being in the conventional and debate conditions. The data sources included drafts and revisions, online statements, perceptual surveys, and interviews. Content analysis was used to assess the students' thinking levels based on the educational taxonomy framework proposed by Anderson et al. (2001). The findings reveal that the students, overall, had positive perceptions of the debate activities. Debating helped them understand the importance of evidence in constructing arguments, broaden their thinking, and gain confidence in composing essays. The students in the debate condition improved their thinking skills more than those in the conventional condition. Nonetheless, a similar improvement did not exist when they were switched to the conventional condition in the second round of writing. Pedagogical implications are also provided.
