While a key goal of engineering education is to prepare students for professional engineering practice, surprisingly little is understood about how and how effectively students make sense of their curricular and extracurricular experiences in order to attain this goal (e.g., how they identify what they have learned from each experience, how they integrate across experiences). With funding from the National Science Foundation, we’ve been exploring this issue by working with students as they create an argument about their own preparedness in the form of a professional portfolio. Earlier research studies, in which we varied the nature of the portfolio, the circumstances under which the students created the portfolio, and the type of data used to understand the significance, have informed the design and issues of interest in the current study-our largest and most rigorous one to date. In this talk I will focus on the design of this current study, what we’ve been hearing from students in the data we have been collecting, and how we have been situating the results in theories of identity construction, transfer of learning, and intellectual capital.