English for speakers of other languages (ESOL) students attending mainstream university courses for the first time struggle with language proficiency issues and have to adjust to unfamiliar pedagogical concepts, including an emphasis on critical thinking. The purpose of this paper is to determine to what extent and to what degree ESOL and mainstream teachers use questions to foster critical thinking skills. This study looks at cognitive level questions, wait-time behavior, use of comprehension checks, confirmation checks and clarification requests, as well as the length, syntactic complexity and cognitive level of student responses. Two advanced ESOL reading/writing classes and two entry-level mainstream writing courses were the sites of this study. Classes were observed and audio-taped with the results transcribed. Transcripts from whole-class discussions of reading assignments and discussions with teachers were analyzed. Tabulations of the question types in each group revealed that the mainstream teachers asked a greater percentage of higher order (i.e., related to critical thinking) questions, though the ESOL teachers asked far more questions. Post-question wait-time was longer in the ESOL classes, and there were far more comprehension and confirmation checks and clarification requests. Both teachers made speech adjustments to help students ask higher order questions. The results confirm that mainstream teachers in low-level writing classes emphasize critical thinking skills whereas ESOL teachers, even in advanced level writing classes, devote class time to both text comprehension and critical thinking. Appendices include both transcription samples and statistical tests. (Contains 49 references.) (KFT)