Using the Community of Inquiry framework, this case study probes the posting patterns of students' social presence, cognitive presence, and teaching presence in an online learning setting. Using purposive sampling, qualitative data were collected from 91 students in the Department of Medical Documentary and Secretary, a fully online associate degree program at a well-known public university. Students participated in six online asynchronous discussion activities on Moodle. The data were analyzed through descriptive and deductive transcript analysis. The findings revealed students' posting behaviors of social presence, cognitive presence, and teaching presence were at a substantially high level, and could be enhanced during treatment fairly significantly. The most important points behind a high level of social presence and cognitive presence were found to be the topics based on real-life cases and scenarios and reflective course activities. The findings further indicated that the difficulty caused by large class size in online discussion could be resolved.