For decades, science policy has been promoting interdisciplinary research (IDR), but universities have not responded uniformly. To explain this variation, we integrate insights from the organizational literature, especially research on microfoundations, and highlight the role of both administrators and faculty. We collect and, with the help of machine learning, code vast amounts of textual data from 156 universities nationwide to measure universities' structural commitment to IDR as well as key explanatory variables, including top-down administrative support for, and bottom-up faculty engagement with, IDR. We integrate these measures with extant data from the Survey of Earned Doctorates, Higher Education R&D Expenditures Survey, NIH, NSF, and IPEDS to analyze how internal university dynamics influence the degree to which a university commits to IDR. Our results reveal that the level of structural commitment to IDR differs at universities with and without medical schools, as do the precursors to this commitment. At universities with medical schools, we find that bottom-up engagement is positively associated with structural commitment to IDR, and that status moderates the relationship between top-down administrative support and structural commitment to IDR. For universities with low levels of supportive administrative discourse status significantly impacted their structural commitment to IDR. At universities without medical schools, top-down support and bottom-up engagement are interrelated and mutually reinforcing such that universities with high levels of both administrative support and interdisciplinary research grants have higher levels of structural commitment to IDR. We discuss the implications of these findings for university administrators, policy makers, and researchers.