This case study was designed to investigate students' perceptions and experiences of the dynamics of online collaborative learning over a semester. Multiple sources of data were collected and triangulated through pre- and post-surveys, personal interviews, group reflection papers, and instructor's observations. Forty-one graduate students enrolled in the same course with the same instructor in two different learning environments - web-based and web-supplemented, participated in the study. The overall results indicated that students in the two environments shared their positive understandings and perceptions about online collaborative learning, which were significantly deepened over time. However, the students in the web-based class were found more positive about the advantages of online collaborative learning than those in the web-supplemented class as their learning experience developed. The study also identified the attributes that were considered crucial to successful online collaboration.