Citizen science projects can serve as constructivist learning environments for programming focused on science, technology, engineering, and math (STEM) for youth. Attributes of "rich environments for active learning" (REALs) provide a framework for design of Extension STEM learning environments. Guiding principles and design strategies for the University of Minnesota Extension's Driven to Discover: Enabling Authentic Inquiry through Citizen Science project demonstrate how education and investigations grounded in real-world citizen science projects can capitalize on REAL environments to generate meaningful STEM learning. Positive evaluation results support the efficacy of the design for enhancing youth science identity and practice.