Despite the fact that teaching is increasingly referred to as a design science, teacher education programs devote relatively little time to developing expertise in the design of instruction, beyond lesson planning. Yet today's teachers not only plan lessons that incorporate existing classroom activities and instructional resources, they also design new learning activities and create their own (technology enhanced) learning materials. Different approaches have been tried to support pre- and in-service teacher design learning. Past efforts to develop teacher skills in design had limited success, probably due to poor alignment of traditional instructional design models with teachers' knowledge, needs and natural ways of engaging with design tasks. More recently, researchers have begun to investigate and develop ways to build on teacher expertise to support them in their design efforts. Yet to date, little has been done to capitalize on what is already understood about teachers as designers nor to draw on the wealth of literature on designers and designing outside the field of education. With the ultimate aim of supporting the work of teachers as designers of technology enhanced learning, this contribution synthesizes research on design from classical design fields, instructional design, and teachers' designing. These perspectives are brought together in an ecological framework that can be used by researchers to study teacher design knowledge and work across projects. This synthesis could also provide an articulated framework for developers and facilitators of teacher professional development programs for identifying key areas for support to teacher-designers in specific settings.