Environmental field days offer a distinct opportunity to connect students with science and the environment. The literature on field days, informed by research on field trips, provides a framework for best practices. If there are best practices, however, then presence or lack of the practice should have a discernible impact on the outcomes of the field day and should be measurable and some of them should be observable. The Delphi process was modified to ground the theory and to end the Delphi using a subset of the panel in a face-to-face meeting to move from consensus to instrument construction. This paper describes the process and shows a summary of the findings of each of the rounds of the Delphi. The use of a Delphi method for determining consensus around the validity of the theory emerging from the research and literature on field days was appropriate and shows that this type of testing against grounded theory can prove useful for building measures to test the emergent theoretical constructs. Modifying the Delphi to focus on the theoretical constructs emerging from the initial analysis allowed the process to function as a true Delphi and eliminated the long process of construct identification. (Contains 4 tables.)