This article illustrates how we incorporated discourse-based interviews (DBIs) into a mixed-methods research study informed by the heuristics of institutional ethnography (IE). As the first stage of a longitudinal study designed to understand what, where, and how "writing" means across our university, our research used DBIs in a writing center to uncover peer tutors' tacit personal knowledge about writing. In tandem with IE methodology, DBIs enabled us to understand how conceptions of writing shape peer tutors' written work and tutoring practice in relation and/or resistance to the programmatic goals of the center. The study demonstrates how the use of DBIs within IE projects facilitates dynamic exploration of the co-constitutive and socially constructed nature of tacit writing knowledge and institutionally coordinated work processes. Our research design and methodological considerations generate strategies and approaches for incorporating variations of DBIs into mixed-methods research.