In this study of curricular and co-curricular learning in STEM disciplines at four liberal arts colleges, comparative analysis of 62 interviews with graduating seniors demonstrates that out-of-class experiences fostered many intellectual, personal, and professional gains. Undergraduate research, in particular, helped to shape science identities and socialize students into the scientific profession. The findings suggest that participation in authentic, independent work with adequate guidance is critical to student learning and development in experiential contexts. (Contains 1 figure and 1 table.)