Learning environments that enable young people to participate in and engage with diverse science, technology, engineering, and mathematics (STEM) practices hold promise for reimagining what counts as STEM and, ultimately, for broadening participation (Eisenhart & Allen, 2020). Out-of-school time (OST) STEM learning experiences have great potential for supporting robust notions of STEM practices and providing opportunities for youth to engage in STEM-linked identity work (Adams & Gupta, 2013; Adams et al., 2014; Bell et al., 2009). In science museum programs specifically, young participants may come to see themselves as part of a broader community that works toward common interests and goals related to science and STEM (Adams et al., 2014). Such recognition by their peers can foster a collective identity (Riedinger & Taylor, 2016) that supports them in navigating difficult challenges as they pursue STEM-related college degrees (Adams et al., 2014). OST STEM learning experiences thus have potential to support participants' interest in and pursuit of STEM. This paper draws on participant interview data and science museum artifacts to understand the relationship between the design of science museum internship programs and the STEM identity work of the participants. The analysis focuses on what it means to be recognized as "a STEM person," participate in STEM-related activities, and pursue STEM interests in science museum internship programs.