While the Two or More Races category has been the de facto mechanism to count multiracial college students since 2010, little research has critically examined how this category has been used in institutional research contexts. Extending previous scholarship on monoracism in higher education, we define "quantitative monoracism" as the policies, practices, and processes by which monoracial categories are elevated and multiraciality is erased in quantitative research. Quantitative monoracism harms those who do not fit monoracial categories by rendering their nuanced needs invisible in statistical analyses. Grounded in quantitative critical race theory and critical multiracial theory, we advance a series of guiding questions and illustrate their application to a case study in hopes of amplifying anti-monoracist action in institutional research.