This article shares lessons learned from a 2-year environmental education professional development initiative with two cohorts. Each cohort consisted of school-based teams of elementary teachers. The professional development included a series of five workshops aimed at integrating environmental education across the curriculum, and each teacher team developed and implemented a school-based project to put these ideas into practice. The project team modified their approach between Cohorts 1 and 2 based on strengths and shortcomings of the first experience. Key takeaways to inform future professional development efforts include ensuring the timeframe of the project allows teachers to build momentum in their work, recruiting teams of teachers with diverse classroom experiences, and including presenters who can offer tangible and actionable ideas to use in the classroom.