A year of COVID-19 quarantine required educators to switch from in-person to virtual learning platforms, causing a dramatic reimagining of their daily praxis. Their experiences are likely to influence new norms for K-12 education. While virtual learning can be effective, student engagement, student retention, and student attention can be challenging. This paper discusses how we adapted a materials-heavy, hands-on, annual summer teacher professional development (PD) program from an in-person to a virtual platform in the initial months of the pandemic. We successfully maintained effective and hands-on components, giving authentic learning experiences to the participants. The 2020 virtual version of the program effectively engaged in-service teachers with high daily participation and retention rates. Nearly all participants rated the workshops as very good or excellent, and an assessment of participants' learning outcomes was comparable to that of the highly-rated in-person 2018 version of the program. Following the PD session, teachers reported feeling more prepared to facilitate their students' learning, increased inquiry-based science teaching knowledge and skills, and their enthusiasm for utilizing workshop strategies. While there are challenges to implementing virtual learning, virtual teacher PD can be widely adaptable and replicable for many institutions, especially in situations in which distance or finances deter in-person participation.