Out-of-school time (OST) science programs, such as the Lang Science Program, play an important role in influencing the trajectory of science learning for many young people. OST programs are especially important for students from groups underrepresented in science, who, more often than not, attend schools with inadequate science education resources. Programs like Lang Science have great potential for young women of color, who often have to grapple with both race- and gender-based barriers to STEM careers. Over the last ten years, OST science programs have multiplied to increase young people's exposure to science. However, there are still not enough opportunities for "long-term engagement," which is essential to move youth from having interest in science to having the skills, knowledge, and self-efficacy to pursue careers in science. This article describes findings from exploratory research conducted to document the experiences of a small group of young women of color who participated in a museum-based OST program during their middle and high school years. The authors were particularly interested in learning how their long-term participation in the Lang Science Program mediated their developing interests and identities as people who like science, understand science, want to do science, and can persevere in STEM majors and careers.