This design-based research study investigates the development of progressive discourse among participants (n=15, n=17, n=20) in three online graduate course contexts. Progressive discourse is a kind of discourse for inquiry in which participants share, question, and revise their ideas to deepen understanding and build knowledge. Although progressive discourse is central to knowledge building pedagogy, it is not known whether it is possible to detect its emergence in the patterns of participation in asynchronous conferencing environments or what kinds of instructional scaffolding are most effective to support its development. This study offers a unique perspective by characterizing episodes of discourse where participants honor the commitments for progressive discourse and by refining designs of peer and software-based scaffolding for progressive discourse. Results showed that measures such as note count, replies, and thread sizes can determine some qualities of online discourse but do not shed light on the development of progressive discourse. Thus an in-depth analysis of discourse for groups was developed to trace the interdependent individual contributions to the group discourse. Peer scaffolding that made norms for progressive discourse explicit was introduced to encourage participants to engage in sustained student-centered discourse for inquiry. Findings show that this intervention was most effective at the beginning of a course for newer online learners and newer graduate students, and least effective for students who were practicing K-12 teachers. A significant barrier to fostering progressive discourse is the tendency for teachers to reject these norms and revert to belief-mode thinking and devotional discourse typical of traditional schooling. Additionally, findings suggest that software-based scaffolding (as found in Knowledge Forum’s scaffold support feature) is a promising avenue for future design innovations to encourage progressive discourse. Although the results of this study are only suggestive, the findings do illustrate ways in which graduate students can uphold the commitments to move beyond expressions of socio- affective connection and opinion to discuss ideas in ways that lead to more useful explanations. The implications for these results for analyzing the quality of online discourse and the designs of instructional scaffolding in online learning environments are discussed.