Workplace competencies describe the skills, knowledge and behaviors students will need to be successful as engineers. Experiential education (co-ops and internships) is critical to the preparation of engineering students as practicing professionals. The experiential workplace is one of the best places for students to develop and demonstrate workplace competencies. At Iowa State University, we have been assessing the workplace competencies of engineering students in the experiential workplace for the past four years. This paper discusses the process by which we identified the most important workplace competencies in partnership with our constituents (employers, faculty, experiential education students, and parents), the assessment tools used, the results across from the last four years, and the implications of these results for engineering education at Iowa State, outcomes assessment and continuous improvement in our curricula.