This paper proposes a new systems development methodology entitled heuristic dataflow diagrams (HDFDs). HDFD leverages group support systems (GSS) and heuristics to improve the creation of DFDs, which are frequently used design artifacts in systems development. We propose theory-based hypotheses to predict likely outcomes of using HDFD in non-GSS groups, GSS groups, and distributed GSS groups. These hypotheses were tested in a laboratory experiment using 123 subjects. The results indicate that HDFD performed with GSS provides process gains over HDFD performed without GSS. Further, distributed groups using GSS and HDFD are able to be as effective as face-to-face (FtF) GSS groups. Our GSS-based methodology of HDFD can be embraced by practitioners to improve the creation of DFDs in FtF and distributed teams and it can likely also be extended to other systems design methodologies, such as structured walkthroughs, entity-relationship diagrams, use cases, and sequence diagrams.