This investigation examines the difficulties encountered by one graduate teaching assistant as she taught "Physics for Elementary Education," a large-enrollment, inquiry-based science course taught at a public Midwestern university. The methodological approach of hermeneutic phenomenology served as the lens to investigate the research question, "What is the lived experience of a graduate teaching assistant as she learned to teach physics through inquiry to elementary education students?" We summarize the findings in terms of the blending of two conceptual frameworks: orientations to science teaching and professional identity. We learned that fundamental beliefs about the nature of science support certain orientations, and if those beliefs remain unchallenged, then the orientation is unlikely to change. Finally, we discuss implications for strategies that may assist college-level instructors with changing their orientation to teaching science.