- For adult learners to succeed in their educational endeavors, adult educators and event planners must meet their needs and goals (Storksdieck, Ellenbogen, & Heimlich, 2005). The learning environment affects how adults learn and what outcomes they achieve (e.g., Hamilton & Tee, 2010; Knowles, 1990; Lim, Morris, & Kupritz, 2007; Young, 2005), so we can help adults by understanding what a successful learning environment entails. To expand our understanding of how adult learner outcomes are shaped by different learning settings, we performed an exploratory study of a non-formal adult learning event. For the past several years the Long Term Ecological Research Committee of the HJ Andrews Forest has hosted HJA Day, a non-formal science education event, in an effort to educate the public about research and educational programs taking place at the HJ Andrews Forest in southern Oregon. The event has traditionally been well attended, but attendance numbers are no longer adequate to represent a successful event. Data from 76 participants was used to answer four exploratory questions about HJA Day: 1) Who are the participants at HJA Day? 2) What outcomes resulted from HJA Day? 3) What experiences and factors impacted those outcomes? and 4) How are those factors and outcomes related? A mixed-method approach was used to determine the main outcomes and the factors that affect those outcomes. We found that HJA Day participants attended HJA Day primarily to learn, network, and spend a day in the forest. Participant outcomes were impacted by three main factors: structural aspects, people and networking, and participants' teaching/learning style preference. The main outcomes that resulted from HJA Day were perceived knowledge gain, change in thinking, overall appreciation, and overall satisfaction. All three factors both positively and negatively impacted the main outcomes. Most participants agreed that they learned, that HJA Day changed their thinking, that their overall appreciation increased, and that they were generally very satisfied with the event. All main outcomes positively and significantly correlated except for overall satisfaction and change in thinking. These findings have implications for the improvement of future HJA Day events, and may inform participant experiences at other adult non-formal science education events. By understanding participant experiences and outcomes, we may aid adults in their pursuits of continuing lifelong learning and help to form a scientifically literate population of responsible decision-makers (Miller, 2004).