With increasing class sizes, teachers and facilitators alike hope for learning groups where students work together in self-contained and autonomous ways requiring reduced teacher support. Yet many instructors find the idea of developing independent learning in small groups to be elusive particularly in K-12 settings (Ertmer and Simons in "Interdiscip J Probl Based Learn" 1(1):5, doi:10.7771/1541-5015.1005, 2006; Simons and Klein in "Inst Sci" 35(1):41-72, 2007). Autonomy in small learning groups is actively promoted in many of the forms of problem-based learning (PBL). A PBL learning group is traditionally defined as students with tutor assigned to the group. However, as PBL is introduced into K-12 environments, the assumption of group autonomous functioning is tenuous for a variety of reasons. The purpose of this research is to determine the extent to which a K-12 PBL learning group functions in autonomous ways when a computer-based scaffold provides some student support normally provided by the teacher or tutor during a PBL environmental science unit. If a computer-based scaffold can successfully enable key elements of autonomous group functioning by supplying process level support normally provided by a tutor or teacher, K-12 teachers anxious to attempt PBL may be able to venture with greater confidence that they can provide multiple learning groups adequate support. Results suggest that a computer-based scaffold informed by Moore's transactional distance theory can promote process elements of autonomous group functioning.