The Environmental STEM (E-STEM) field experience reimagines the traditional undergraduate geology field course as a field and career preparation program for first- and second-year students interested in environmental careers. We developed a new field course model that includes geology, geomorphology, hydrology, and botany field projects in the Sierra Nevadas, CA; interaction between students and local environmental professionals ("stakeholders"); and post-field career activities. As a multi-institutional collaboration, the E-STEM program united a diverse group of learners in 2017 and 2018. The E-STEM curriculum focuses on the technical and interpersonal skills that were identified by environmental professionals as beneficial in a variety of environmental careers. The Sierras field course was followed by professional development activities hosted at each of the three institutions. Additionally, a badge system highlighting key skills was developed for use by the wider E-STEM community.