Research indicates there is a need for teachers to experience multiple mastery experiences with engineering teaching in order to improve teaching engineering self-efficacy. To prepare future K-5 teachers to teach the engineering design process, one science methods course integrated 2-day engineering mini-units into the class meeting and school-based field experience. The preservice teachers participated as students in an exemplar mini-unit and then designed their own mini-unit, which they later taught to K-5 students. Pre- and post-testing of the preservice teachers indicated significant improvement in engineering pedagogical content knowledge self-efficacy, engagement self-efficacy, and disciplinary self-efficacy. Significant improvement was not observed in engineering outcome expectancy.