Community-Based Learning (CBL) within the science, technology, engineering, and mathematics (STEM) fields has the potential to support student learning outcomes while also promoting beneficial outcomes in partner communities, yet complexity of practice can often obscure or limit these outcomes. The multiple participating stakeholders, variety of interactions and settings, and differing goals and objectives, lead to emergent behavior. These dynamics make outcomes, especially those for the community, difficult to recognize. A systems-level approach which clarifies the structure of CBL can minimize some complexity, yet empirical evidence of how STEM CBL is structured in practice is limited. The National Research Council has established a three-tiered model in which Community, Program, and Individual levels provide a structure for informal STEM learning. In this work, this structural framework is used to analyze two case studies to answer the research question: How do the three system levels (Community, Program, and Individual) describe the STEM CBL practitioners, their actions, and goals? Findings from a thematic analysis of data generated through participant-observation within the two purposefully selected cases establishes a foundation for how these system levels can impact practice. Findings indicate that these three levels provide benefit in characterizing STEM CBL and the dynamics between stakeholders. Practitioner awareness of the levels and their implications can promote clarity on the roles, actions, and outcomes for practitioners. Distribution of effort across the three levels can support well-rounded CBL practice through promoting a balanced approach to CBL needs, as well as advancing the voices of all practitioners, but especially those with less power.