In this case study, we used a mixed-methods approach to identify the characteristics of environmental education (EE) lessons most positively associated with students' environmental literacy outcomes at one residential EE center in the U.S. Students attending residential EE programs spend multiple days participating in numerous lessons, activities, and experiences, resulting in perhaps more opportunities to enhance students' knowledge, attitudes, skills, and behavioral intentions related to environmental literacy. To explore what teaching approaches were most effective at enhancing immediate student outcomes and to provide insights for practitioners, we observed 80 lessons, tracked 20 observable teaching approaches, and administered questionnaires to measure students' self-reported changes in environmental literacy outcomes. Correlation analyses revealed four variables related to enhanced student outcomes: affective messaging, environmental issue-focus, relevance, and effective time management. Two variables, fact-based teaching and data collection, were negatively correlated with student outcomes. Linear regression analysis with these six variables resulted in a model explaining 34% of the variance in the environmental literacy outcome. We discuss these findings and share examples of each practice from our qualitative observations. We also discuss broader applications of our mixed methods approach for the field.