This paper describes a professional development model with promise for supporting meaningful shifts in practice. We begin by introducing the theoretical principles underlying our professional development model, with a focus on explicating the interface between collaborative inquiry in a learning community (Lave, 1991, In L.B. Resnick, J.M. Levine, S.D. Teasley (Eds.), Perspectives on Socially Shared Cognition, American Psychological Association, Washington, DC; Lave, & Wenger, 1991, Situated Learning: Legitimate Peripheral Participation, Cambridge University Press, Cambridge) and teachers' self-regulated learning. Next, we report on successes and challenges within a 2-year collaborative research partnership. We recount how participating teachers reflected on practice, constructed conceptual knowledge about teaching, and made important instructional shifts. We also detail features of our model that teachers found most effective. We close by discussing our implications for theory and in-service professional development.