The complexity of engineering and its integration into K-12 education have resulted in a variety of issues requiring sustained empirical research (Johnson, Burghardt, & Daugherty, 2008). One particular area of need, given the emphasis on teacher effects on student learning, is to research engineering-oriented teacher professional development. A lack of publications on the effective practices of engineering-specific professional development projects makes a study investigating mature efforts necessary. Thus, the purpose of this qualitative study was to explore professional development elements for secondary school engineering education. The research questions that guided this study were: (1) What are the primary design elements used to deliver engineering-oriented professional development (logistics, format, activities, instructors, and instructional strategies) and why were these elements selected?; and (2) How do the projects define and evaluate effectiveness? The focus on the professional development design decisions and determinations of effectiveness for secondary school engineering education are particularly important because they are the elements that "designers of professional development have immediate control over and can modify in order to increase their impact on teachers' knowledge, beliefs, and attitudes, and subsequent enactment" (Fishman et al., 2003, p. 646). Each design decision is typically connected to a distinct purpose and level of impact (Speck & Knipe, 2005). By understanding the design decisions of specific projects, the connection to secondary school engineering and its impact on teaching and student learning can be better understood. (Contains 2 tables.)