In this paper, I study the effects of quantifying knowledge on the organization of disciplinary fields. Using an original dataset of about 44,000 British social scientists and bibliographic information about their published, peer-reviewed articles, I show that the introduction of standardized research evaluations disrupted local academic labor markets in British higher education, leading to patterns of interinstitutional mobility that altered the epistemic diversity of social science disciplines and the organization of their academic fields. Much like market-based interventions, research evaluations lead to a form of epistemic matching that has distinct consequences on how knowledge is generated. In particular, when evaluations affect organizational units (such as academic departments) and stress disciplinary norms, they foster forms of isomorphism that lead to reductions in a discipline’s thematic diversity and a more homogeneous structure for the field. This paper thus advances the sociology of knowledge by showing how epistemic change occurs not only through the individual realignments of quantified scholars but, as importantly, through the mediation of interinstitutional mobility.