Learning to monitor and regulate one's learning in an academic setting is a task that all students must engage in. Learning in "group" situations requires both self- and co-regulation. This research examines a case study of a small group of medical student interactions during an on-line problem based learning activity (PBL) where students learn to co-regulate their performance as they construct their understanding of how best to communicate bad news to patients. This paper introduces an approach for analyzing the group discourse to understand how collective knowledge building facilitates co-regulation. A mixed method analysis was used to analyze the case study data. A qualitative data analysis of verbal interactions was conducted to examine co-regulatory episodes. Collective knowledge building was examined by analyzing the group discourse for indicators of co-regulatory processes. The study follows two quantitative analyses: a frequency count analysis of types of questions asked by facilitators and students; and a sequential pattern mining for patterns of co-occurrences of learners' discourse and co-regulation.