Despite the complexity of facilitating professional development (PD) and growing attention to supporting facilitators, few tools exist for facilitators to engage in ongoing inquiry into their practice. In this article, we offer a practical measure, the Collaborative Professional Development Survey (CPDS), designed to provide facilitators with information about teachers' perceptions of aspects of the PD learning environment that research indicates matter for teachers' opportunities to learn. We illustrate how facilitators used the CPDS to support their collective inquiry into facilitation. We also illustrate the social processes that appeared to enable facilitators' productive use of the CPDS, including a routine to analyze the resulting data, and the orientations that underpinned their analysis. We discuss implications for facilitators' use of the CPDS.