This paper presents a case study of how librarians can situate themselves as pedagogical partners by bringing their unique information literacy perspective and expertise to the programmatic assessment process. This report resulted from the Thun Library and the Penn State Berks Composition Program's collaboration to assess the institution's first-year composition (FYC) course. From previous programmatic assessments of their students' work, the faculty knew that students struggled with source use in their rhetoric but found it difficult to pinpoint students' exact source issues. By adapting a rubric theoretically-grounded in the ACRL "Framework" to deconstruct the concept of source use into four categories, librarians developed a rubric that illuminated source engagement problems on a more granular level than the programmatic assessments conducted without librarian involvement, leading to specific suggestions for addressing issues with student source engagement