Project-based learning (PBL) is a long-standing curricular model that has been argued to support equity-based goals in science learning. Yet, little is known about how PBL can be implemented effectively and equitably in the context of virtual instruction. This comparative case study follows two elementary science teachers as they transition to virtual instruction at the beginning of the COVID-19 pandemic. Drawing from classroom observations and interview data, we highlight the opportunities and challenges of virtual PBL instruction, with a focus on the features of PBL and the equitable engagement of all students. Findings show that teachers maintained the four features of PBL in virtual instruction, but prioritized different features in response to their own equity goals: Amy, a 5th grade teacher, prioritized collaboration, and Irma, an ELD instructor, prioritized connections to home and community. We draw implications for the development of PBL curriculum, in both in-person and virtual instruction, and highlight the value of teacher agency in supporting the ongoing evolution of the PBL curricular model.