In this article, we examine the promise of a popular set of sentence stems, "I notice" and "I wonder," for fostering productive discussion in an online course for teachers. Drawing on teachers' responses to one another's classroom reflections, we look for evidence regarding how course prompts encouraging teachers to use these stems influence the types of contributions teachers offer. We analyze teachers' responses at the module, response, and sentence level, situating our inquiry in the context of common challenges related to discourse in teacher professional learning contexts. Our findings suggest that prompting teachers to report what they "notice" and what they "wonder" may support the development of teachers' professional vision and exposure to diverse perspectives.