This paper presents the results of the implementation of an instructional approach that supports teachers' learning of instructional design (ID) and honors their beliefs and concerns within the ID process; participants included two instructors and 23 practicing K-12 teachers enrolled in an instructional design course as part of a masters program. The theoretical framework that supports this inquiry is presented, including how ID is viewed and consequently taught (the designer's view), how ID is used by teachers (the teacher's perspective), collaboration between teacher and designer, and teacher inquiry into their teaching. The research method is described, including the co-participatory, reflexive approach to instruction, in which all participants were viewed as learners who continually reflected and appraised joint efforts at teaching and learning ID. Findings are summarized and related to ways that teachers used to describe and represent their practice in ID projects, personal ID models, and course evaluation. How the co-participatory approach helped teachers and designers to learn from each other is discussed. (Contains 50 references.) (MES)