Collaborative design is recognised as being shaped by complex social, cognitive, material, and technical processes. In the case of design decision-making, however, the social dimension has yet to be fully understood as the product of the whole team dynamic rather than as simply the sum of the individual (cognitive) contributions. This paper examines the interactional work teams of first-time design students do that produces decisions in undergraduate engineering design projects. Close analysis of decision-making episodes, recorded in design meetings in a yearlong ethnographic study, reveals the joint social and situated work teams do to produce decisions. Students were found to do decision-making via three overlapping phases that were invariant across the database: (i) Design options emerge, (ii) teams orient to design options, and (iii) design decisions come off. This paper exemplifies these phases of decision-making as "inherently" -- and not just incidentally -- social, and illustrates how decisions are produced in novice design teams via these phases in multifarious ways. We argue for an explicit retrospective focus on the processes and consequences of team decisions following projects as an avenue for fostering the development of design judgment that engineering graduates will take into their professional practice.