Teachers in professional development (PD) programs need time to adopt, enact and reflect on what they are learning in the PD within their own situations. To encourage reflective implementation and adaptation of ideas and practices promoted in the PD studied in this article, participants were asked to engage in several small action research projects over time. To gain insights into how the cyclic process of implementation and reflection effected changes in practice and knowledge, we examined the nature of the research questions asked by a cohort of teacher-researchers (n=31) as they engaged in several cycles of action research over a three-year period. We found the nature of the questions they asked shifted over time from investigating the efficacy of particular interventions in terms of students' performance to exploring how to support students as they reason about mathematics. These results provoke questions about why these particular changes occurred and why others did not.