Background: Design problems have long attracted researchers' attention for their potential to provide authentic learning opportunities. While we have methods for supporting students to learn through relatively simple engineering and design tasks, supporting students to address complex problems that they find and frame remains poorly understood. Designing for the real world presents opportunities to understand how heterogenous engineering practices emerge from students' experiences, how problems are negotiated and reframed, and the forms of learning such experiences support. Descriptions of engineering practice often privilege technical aspects, where heterogeneous engineering emphasizes the active coordination of social and material dimensions as well. Methods: We present two cases from large, complex design projects: (1) a design-based research study in a school-based making space and (2) an extended participant observation in a design-build school. We used interaction analysis to characterize the forms of participation. Findings: We identified ways students negotiated social and material elements of design, how they coordinated these activities, and how the instructional environments contributed to developing heterogeneous practices. Contribution: Designers and materials both operated as agentive actors in dialogic conversations that coordinated the multitude of considerations involved in heterogeneous engineering. We argue for the importance of fostering sociomaterial entanglements to support learning in design.