A comprehensive assessment plan is a valuable component of a university’s K—12 outreach effort. The K—12 Engineering Outreach Initiative has integrated an assessment plan into each stage of its outreach—development, implementation, and sustainability—with the ultimate goal of expanding the pool of youngsters who imagine and prepare themselves for futures in science, engineering, and technology. Outreach objectives were assessed by formative and summative assessment tools. The comprehensive assessment plan developed provides an analytical structure for guiding workshop development, shaping implementation, measuring success, and informing future planning. Lessons learned during this program are discussed.