Developing innovative science, technology, engineering and mathematics (STEM) curricula that elicit student excitement for learning is a continuous challenge for K-12 STEM teachers. Generating these lessons while meeting conflicting pedagogical objectives and constraints of time, content, and cost from various parties is truly a challenging task for any teacher. Recognizing the parallel between curricular design and engineering design, we posit that the engineering design process (EDP) can be used as an innovative, effective, and logical means for formalizing the development of K-12 STEM lessons. The use of the EDP as an instructional development (ID) model is firmly based on the existing literature theory of how people learn; in particular, identifying the students and teachers as clients for the design process is a learner-centered approach, and problem-based learning (PBL) encourages active learning of STEM concepts in the context of authentic problems. To develop this process in practice, we collaborated with 15 middle school teachers over three years to create active learning curricular modules to teach over 2,000 students difficult STEM concepts. This article describes the practice of how teachers can utilize the EDP to develop problem-based curricular units and in doing so become more comfortable with the EDP themselves. We also report on the evaluation of this project.