Which approaches are associated with better student learning outcomes in environmental education (EE)? We observed a sample of 299 day-long EE field trip programs occurring across the U.S.A. for youth in grades 5-8 (ages 9 to 14). We tracked the extent of use and quality of implementation of 66 programmatic, educator, and setting characteristics and measured student outcomes immediately after the programs using a retrospective survey. A series of complementary tests identified 11 characteristics that were most powerfully and consistently associated with learning outcomes, accounting for 18% of variance in learning outcomes. These included group size, naturalness, novelty, place-based pedagogy, verbal engagement, quality questions, transitions, and staging, as well as the responsiveness, comfort and clarity, and emotional support provided by the educator. Some of the most commonly promoted practices in the EE field were rarely observed. Implications are discussed for both practice and research.