Undergraduate field experiences (UFEs) are a prominent element of science education across many disciplines; however, empirical data regarding the outcomes are often limited. UFEs are unique in that they take place in a field setting, are often interdisciplinary, and include diverse students. UFEs range from courses, to field trips, to residential research experiences, and thereby have the potential to yield a plethora of outcomes for undergraduate participants. The UFE community has expressed a strong interest in better understanding how to assess the outcomes of UFEs. In response, we developed a strategy by which practitioners can assess their UFE using an evidence-based, systematic and iterative approach. This essay guides practitioners through the steps of: identifying intended UFE outcomes, considering contextual factors, determining an explicit assessment approach, and using the information to inform next steps. We provide a table of common learning outcomes and potential assessment tools, vignettes to illustrate using the strategy, and suggestions for practical application of the strategy. We aim to support comprehensive and aligned assessment of UFEs, leading to more inclusive and reflective design, and ultimately improved student outcomes. We urge practitioners to move towards evidence-based advocacy for continued support of UFEs.