Promoting the participation of under-represented minorities in engineering is a national imperative. Focusing on elementary school students is critical for broadening participation in engineering, as many children form lasting beliefs about their STEM identities and STEM self-efficacy in elementary school. While there has been a recent surge in efforts to integrate engineering in curriculum in traditional school settings, out-of-school settings continue to play an important role in promoting equity in pre-college engineering experiences. Out-of-school settings in particular can be ideal for providing children with culturally-relevant engineering experiences. This project focuses on the National Society of Black Engineers (NSBE)'s Summer Engineering Experiences for Kids (SEEK) program. This multi-partner project allows us to expand and strengthen the experience, conduct research on the impact of the program, and conduct research on how such outreach programs might grow in sustainable manners. Our poster will present a summary of the large-scale data collection that occurred during the summer of 2018 at all 16 sites located across the US. We administered a variety of instruments to identify changes in the children's STEM-related outcomes over the course of the SEEK experience. To further operationalize the variation in organizational contexts across sites, we collected data from parents and mentors. In the poster we will share information about the instruments used for this study. Additionally, our poster will summarize the work that we have done to further strengthen the curricular and training aspects of SEEK.