This article offers one potential response to Yancey's (1999) call for a fourth wave of writing assessment able to capture writing development in all of its complexity. Based on an ecological perspective of literate development that situates students' growth as writers across multiple engagements with writing, including those outside of school, the ecological model of writing assessment described in this article seeks to provide students, teachers, departments, and institutions with fuller, richer accounts of the breadth of students' literate experiences and how those experiences impact their abilities to accomplish academic tasks throughout the undergraduate years and beyond. Using the University of Central Florida's recent efforts to develop and employ an ecological assessment model as one of many potential examples, this article argues that an ecological model of writing assessment enables institutions to make visible the multiple sites where writing takes place, strengthen the affordances for student learning and writing in these sites, and also respond effectively to the multiple stakeholders invested in understanding writing development, what it involves, and how it might best be supported.