Reflexivity has gained considerable significance in organization studies over the last decade. The discussion provides significant insight into interpreting one’s findings and into presenting them to the academic community. But, the relationship between research partners in practice and researchers remains less in focus. Nevertheless, it provides the foundation from which data and interpretations emerge. To provide an orientation, this paper aims to develop a methodological heuristic inspired by social systems theory to conceptualize the relational foundation of longitudinal research. This “reflexive system theory heuristic” is illustrated empirically by reconstructing the research process of a longitudinal single case study on a change process in a hospital. The heuristic helps to observe and explain the dynamic relationship in the field and to explicitly acknowledge the status of empirical findings when understanding research as a generative activity. The heuristic conceptualizes the researched and research practices as communication systems, thus consistently developing a reflexive approach for field research. By taking into account the practice as well as the academic context, the heuristic can be extended to the insights drawn from the discussion on reflexivity. For social systems research on organizations, the heuristic provides a starting point to foster a methodological discussion.