Teaching writing well poses several challenges in today's diverse classrooms. Despite a growing research base on teaching writing, outcomes for students with disabilities in secondary schools continue to be disappointing. Research in the naturalistic tradition that would help educators understand the knowledge and beliefs that influence teachers' practice, however, is scarce. Specifically, researchers know little about how exemplary general education teachers, who often have little to no training in special education, think about writing instruction for students with disabilities. To investigate teachers' understandings and practices for supporting students with disabilities, interviews, observations, and artifacts were analyzed using qualitative methods. Exemplary teachers' understandings of writing instruction for students with disabilities who are included in 9th- and 10th-grade general education language arts classes included deep and integrated knowledge of content and pedagogy that enabled them to facilitate the students' progress. Teachers had firm beliefs that (a) students with disabilities could make progress and (b) learning writing was vitally important. Teachers' understandings of writing instruction for students with disabilities were influenced by their knowledge of content and pedagogy, their beliefs about students and writing, and the contexts within which they worked. Implications include a call for more research about (a) the relationship between teachers' beliefs and their practices, (b) opportunities to engage in context-embedded professional development, and (c) the amount of time necessary to reflect on, respond to, and deliver meaningful feedback in a sustained dialogue about writing for students with disabilities.