Collaborative watershed management has been heavily promoted and widely implemented to address a variety of natural resource concerns, resulting in the adoption and adaptation of the approach to management by regulatory agencies. Although several characteristics or indicators of success for watershed partnerships have been identified in the literature, these often portray a direct cause and effect relationship between partnership characteristics and outcomes. However, partnerships involve dynamic processes that can be influenced by both form and function (internally and externally) throughout various stages of the partnerships' existence. Our study presents an evaluation framework from the group process and evaluation literature to highlight the importance of evaluating ‘intermediate measures of partnership effectiveness’ in watershed partnerships, using the case of Michigan's voluntary watershed-based stormwater permit. Given the increasing use of watershed partnerships in a regulatory setting that is constantly in flux and the difficulty in assessing the effects of such groups on water quality, results suggest the utility of ‘intermediate measures of partnership effectiveness’ for assessing partnership process in order to provide ongoing feedback and incentives to ensure long-term success.