In this paper, we examine the role of reflection in teacher preparation, specifically within a mentoring relationship between cooperating and preservice teacher. We report findings from a case analysis of this pair who engaged in problem-posing dialogue within pre- and post-conferences around practice over one year of their work together in an elementary-level classroom. The context is an innovative programme in which cooperating teachers pursue their Master's degree while undergraduates (preservice teachers) complete their elementary education degrees. Our analysis of talk about teaching during six coaching cycles as well as supporting documents illustrates how Jane's mentoring supported reflective practices and disrupted a notion of a field experience as simply a place to "practice" pedagogical knowledge with corrective feedback. Additionally, we explore the tensions in this approach to mentoring. This case study has implications for teacher educators who seek to bolster teacher preparation through the support of mentoring relationships.