The facilitator plays a key role in guiding students' efforts during case discussions. However, few studies have compared differences in learning outcomes for students participating in facilitated versus non-facilitated discussions. In this research, we used "problem space coverage" as a learning measure to compare outcomes between facilitated (F) and non-facilitated (NF) online case-based discussions. In general, results demonstrated both greater and deeper problem space coverage during facilitated discussions. More specifically, students in the facilitated discussions tended to discuss more aspects of the problem space in more detail, and spent more time on relevant instructional design issues and related solutions than students in the NF discussions. Overall, results illustrate the role of discussion in addressing the targeted problem space during case-based learning while underscoring the role of the facilitator in enabling that coverage.