Collaborative learning theory points to knowledge construction as an outcome of peer interaction, justifying widespread implementation of collaborative activities (like small group discussion) that scaffold toward individual writing projects. This article offers a qualitative investigation into the process of collaborating with peers and the extent to which peer interaction facilitates knowledge construction. More specifically, I present two case studies from FYC courses, one of a debate activity that successfully facilitated knowledge construction and the other of a Google document activity that was not successful. The methodology--triangulating interviews, observations, and an analysis of student writing--presents a replicable strategy for measuring knowledge construction as a result of peer interaction in FYC. I analyze these findings in light of the Community of Inquiry Framework, arguing that the knowledge construction (cognitive presence) that resulted from the collaborative activities I observed was supported by the instructor emphasizing multiple perspectives in the activity design (teaching presence) and establishing a strong sense of community (social presence).