Given the complex nature of learning and behavior change, the success of environmental education in a global world depends on educators continually adapting and creating new practices, forming practice-sharing networks, co-creating knowledge, and fostering intercultural understanding. Massive Open Online Courses, or MOOCs, can contribute to these professional development strategies for environmental educators, who in turn co-create artifacts to advance the field more broadly. However, MOOC research to date has largely focused on course learning analytics and completion rates rather than individual practice or broader field level outcomes. We conducted a survey of participants (n=643) in seven environmental education MOOCs offered by Cornell University to answer the following questions: (1) How do MOOCs influence participants’ educational practice change, ongoing professional networks, and global engaged learning? and (2) How do participants co-create knowledge that is useful beyond the MOOC?. The results show that MOOCs can be effective in building environmental educators’ capacity and helping them contribute to their professional field, yet such impacts vary due to educators’ prior networks, language barriers, and other factors. We present the results in terms of a model of broader outcomes for MOOCs that address wicked problems such as environmental stewardship and behavior change.