This mixed methods study examined how engagement in robotics and game design influenced students' self-efficacy, STEM attitudes, and computational thinking (CT) skills. Predominantly African-American students engaged in engineering and computer science tasks during informal learning environments. Results revealed students' self-efficacy scores on computer gaming increased significantly. Focus group data supported these findings, revealing that computer programing was challenging, but students enjoyed the tasks, added elements of culture in some cases, and valued the agency the tasks provided. Focal students were also able to make connections to STEM-related careers. Observational data demonstrated that focal students exhibited substantive CT during robotics and moderate CT during game design. Results support the idea that robotics and game design may be used to broaden underrepresented students' participation in STEM.