In this study, we investigated the effects of students' participation in a collaborative, project-based engineering design course on their domain knowledge, interests, and strategic processing. Participants were 70 college seniors working in teams on a design project of their choosing. Their declarative, procedural, and principled knowledge, along with their domain interest and their interest in select roles within that domain were tested at the outset of the semester and at its conclusions. Findings indicated that this course contributed to a rise in students' declarative knowledge, but not their procedural or principled knowledge of engineering design. Further, there was no significant change in students' personal interest in the domain over the semester, and their role interests were not associated with their demonstrated knowledge in the field at posttest. Implications for the perceived effectiveness of learning environments consisting of peer collaboration and relevant problems on students' academic development are considered.