The theory of participatory action research (PAR) grew out of the practice of problemsolving in groups and organization by involving the participation of all pertinent stakeholders in decisionmaking process through empowerment. The ontological assumption is that "the world out there" is defined by the participating stakeholders as they understand and perceive it. Theactionable knowledge thus produced is mostly used subjectively in the hope of a favorable organizational change or a transformation for betterment. On the other hand, Management Science/Operations Research (MS/OR) is more concerned with epistemological objectivity in identifying and defining managerial issues and finding solutions. In this paper we shall show that MS/OR can benefit from and contribute to PAR in complex decision making contexts. This kind of mutual benefit will beillustrated through a study reported in the area of R& planning. It will be shown that PAR "contextualizes" problem structuring whereas MS/OR "optimizes" the consensual decisionmaking process in a multiorganizationalcontext.