This qualitative case study describes how participation in an outside-of-school program sustained middle school girls' interest in computer science and positively influenced their computational perspectives. Data consists of interviews, observations, and videos analyzed from ten girls participating in a nine-month program during 2017-2018. Connected learning and computational participation are the study's theoretical frameworks and were incorporated into its research questions, data collection methods, and analysis strategies. Findings illustrate (1) girls' sustained interest in and positive attitudes toward computer science; (2) girls' evolving confidence and awareness of computational perspectives; and (3) the importance of group work in nurturing girls' computational participation. This study contributes to the research on strategies for addressing the gender gap in computing through providing informal learning opportunities for young girls.