Writing Program Administrators consistently witness the importance and effectiveness of interdisciplinary writing instruction, but convincing others that such a pursuit is worthy of campus-wide investment is a challenge. University stakeholders come from a variety of disciplines and are thus convinced by different forms of arguments and data. This paper shows how one large university writing program approached its own program assessment in an effort to convince multiple stakeholders of the program’s effectiveness to improve critical thinking and writing across the disciplines. The authors conducted a mixed-methods case study of two writing intensive (WI) courses in order to explore student writing and student/faculty perceptions of their WI experiences. The authors found that students significantly improved across written drafts and held highly positive feelings toward their courses and their WI experiences. Furthermore, students identified the benefits of WI courses, such as the value of authentic writing assignments, the critical thinking required of their assignments, and the improvement of their conceptual thinking. The authors argue that such a mixed-methods approach is a powerful means through which writing program administrators can show the effectiveness of their university writing programs.