In this instrumental case study, we examined the ways in which one mathematician's instruction unfolded during his participation in a faculty collaboration geared towards reforming instruction. In the study, we offer the case as both the participant's collaborative experience in an online faculty collaboration and his implementation of an inquiry oriented differential equations curriculum at the same time. The faculty collaboration specifically focused on reforming instruction to align with inquiry oriented instruction. Data analyzed for the case study included recordings of the weekly faculty collaborations, video observations of the participant's instruction over a full semester, and interviews that focused on the participant's perspective of his experiences. Results indicated the participant was very capable of eliciting student ways of reasoning and other student contributions from his class but he less often actively inquired into their thinking. This was either because he had already anticipated their thinking, or was not attentive to it because his mathematical opinion took precedence in his thinking over that of his students. Further, results indicated that from the participant's perspective, the online faculty collaboration supported him in his instructional reform endeavors by providing him language to define his instruction. It also provided him avenues to engage in pedagogical discussions and experience, through the other participants, different ways students thought about differential equations.