This paper presents an analysis of engineering students' use of Design Heuristics as part of a team project in an undergraduate engineering design course. Design Heuristics are an empirically derived set of cognitive "rules of thumb" for use in concept generation. We investigated heuristic use in the initial concept generation phase, whether heuristic-inspired concepts were carried through to later design process stages, and how concept synthesis within each team's design process related to heuristic use. The results reveal widespread use of Design Heuristics among the concepts generated by individuals and selected by teams for further development, and a prevalence of concept synthesis within approximately half of the observed teams' design processes.