Quantitative reasoning (QR) competencies are increasingly called for in the data rich and complex environment of STEM disciplines, including biology. Curricular reform efforts in QR have been directed at disseminating course design and pedagogy but less work has been directed at understanding what faculty at large view as crucial for student success in their courses. We conducted semi-structured interviews of 15 faculty teaching in an introductory biology course sequence to determine (1) what participants viewed as QR competencies crucial for student success, and (2) their perceptions of student preparedness for QR in context. Participant responses fell into four categories (Quantitative Reasoning, Process of Science, Modeling, and Affective Factors) which largely align with competencies called for in recent publications. Additionally, participants noted that many students lacked these QR competencies upon matriculation. Characterization of QR skills crucial for success can help guide curricular reform not only in biology, but also in the context of other STEM disciplines.