We explain how collaboratively assessing a writing-intensive general education capstone seminar constituted a high-impact practice for faculty development. Students at the University of Denver complete an Advanced Seminar taught by faculty across the curriculum. Topics and themes vary widely, as do types of assigned writing, making assessment an ill-defined problem. Eleven professors each collected complete writings from five students, then met with the authors in a workshop to code and analyze these 468 artifacts. Participants also interpreted student questionnaires (both multiple-choice and open-ended questions) and wrote analyses of their courses. We present findings about the length, types, genres, and purpose of writings. We also present themes emerging from the workshop and analyses, most notably concerning mixed writing purposes and the tension professors saw between "standard" and "creative" assignment making. The assessment process fostered rich insights about individuals' teaching as well as about the nature of writing across the seminars.