There is an increasing interest in the field of experiential education to move beyond simply documenting the value of experiential education programs and, instead, develop more evidence-based models for experiential education practice (cf., Gass, 2005; Henderson, 2004). Due in part to the diversity of experiential education programs, participants, goals, designs, and specific program experiences, there exists a broad constellation of variables that can impact the results of studies using an evidence-based approach. While many of these variables are accounted for through effective research designs, others are largely uncontrollable, yet remain influential. These uncontrollable variables can often distort or confound the results from research and evaluation efforts. This paper categorizes some of the most common confounding variables into three temporally based categories: Precursor, Concomitant, and Postexperience. Following this, suggestions for researchers and evaluators in addressing these variables are provided.