This paper describes a learning outcomes assessment of students who have participated in the ASABE 1/4 Scale Tractor Design Competition. The "lllini Pullers" in the Department of Agricultural and Biological Engineering at the University of Illinois at Urbana-Champaign have been engaged in this tractor design competition since 2000. Faculty and corporate supporters indicate that student participation in this organization appears to cultivate qualities that The National Academy of Engineering emphasizes in its vision for the "Engineer of 2020," such as communication, teamwork, and business skills; flexibility; professionalism; and creativity. Engagement in co-curricular activities has been shown to positively affect students' educational persistence and attainment, and preliminary evidence indicates that such engagement contributes to engineering students' professional preparation. However, specific outcomes of participation in particular organizations are rarely assessed or documented. Therefore, in this paper we first describe surveys and interview protocols used to elicit students' reflections and perspectives on their learning experiences in the lllini Pullers. We then share findings that elucidate the nature of the skills, knowledge, and attitudes that participants develop through this club and competition. Data from surveys of alumni of this organization provide insights into the longer-term impact of their experiences on their professional lives. Implications are considered at two levels: (1) What desired attributes of engineers are developed via participation in the lllini Pullers? (2) How can students and other stakeholders benefit from the learning outcomes assessment process?