This study investigated graduate students' perceptions of the online collaborations and the factors that contribute to the quality of online discussion with a qualitative case study. Data were collected through interviews with 20 graduate students in an online course, their online discourse, and the instructor's observation notes. The case study found out that manner of response, size of the group, and the topic of discussion in the online discussions were identified by the students as the important factors that determined the quality of online discussions. From students' perspective, this study helped identify patterns in which online discussion is conducted in conjunction with course context and individual characteristics for enhancing learning growth. Knowledge of such patterns can facilitate new designs and improvement of online collaborative learning. (Contains 1 figure. Interview Questions are appended.)