DescriptionComputer technology is used as a mediational tool to support collaborative instructional methods. Computer support offers a platform for collaboration with the goal of scaffolding students’ understanding, providing increased agency to the student for their own learning, and motivating students, as participants in a PBL process. In online PBL, ideas are made visible in the online environment where students can create iterative processes over time to build problem solutions. Research on face-to-face collaborative discourse in education is fairly extensive. However, with the relatively new and growing use of online collaborative learning, collaborative learning in this context has been given only modest attention to date. The primary research question was: What are different patterns of knowledge construction as part of collaborative discourse? This qualitative case study examined data from 34 students enrolled in an undergraduate course in an educational psychology. The course used a blended instructional structure of in class face to face time and asynchronous online problem-based learning (PBL). Students were assigned to collaborative working groups (n=6 groups). Four online PBL cases were presented and each group was assigned a facilitator (the course professor and a graduate assistant). The students had to collaborate to develop and present a problem solution to each of four problems – posting their dialogue online. The online dialogue was analyzed for characteristics of participation, interaction, and student learning. The goal of this case study was to illuminate and understand the characteristics of online knowledge construction. Examination of the collaborative problem-solving process revealed examples of discourse that showed evidence of both individual learning, social construction of knowledge, and the collaborative knowledge building of a group. Groups that demonstrated a more interactive style of interaction and worked to negotiate a shared understanding of the problem solution were able to integrate educational psychology at a more elaborated level. Through this descriptive process the findings add to a growing body of knowledge about computer supported collaborative learning and PBL and can help to support effective instructional designs and practices.