Co-teaching has recently gained popularity and attention as a viable service delivery option for students with disabilities and other special needs. Although co-teaching includes the three components of co-planning, co-instructing, and co-assessing, the professional literature has primarily focused on co-planning and co-instructing. Co-assessment, however, allows teachers to collaborate by differentiating instruction based on students' present levels of performance and monitoring progress as required in Response-to-Intervention systems. These positive outcomes occur when co-teachers share assessment responsibilities before, during, and after instruction. In this article, we describe a variety of assessments and highlight ways that co-teachers can differentiate learning and assessment outcomes. (Contains 1 figure and 1 table.)