<p>Societally beneficial behaviors often have to compete with alternative behaviors for limited resources (e.g., time). Every minute invested in helping others, the community, or the natural environment cannot be invested in the pursuit of hedonic pleasure or economic profit. Yet existing behavioral paradigms and experimental models rarely consider the activities competing with the societally beneficial behavior of interest. Here, we developed the Behavioral Allocation Task (BAT) to explicitly model the opportunity costs of pro-environmental behavior. On each BAT trial, participants can decide whether they want to use the next 30 s to generate environmental benefits, to work for their own financial benefit, or to engage in a potentially more hedonic activity (i.e., watching videos). A preregistered experiment (<i>N</i> = 228) showed BAT choice behavior to systematically track the value of those behavioral options. Pro-environmental choices became more likely when they led to larger environmental benefits, but also when the competing behaviors decreased in value. Individual differences in BAT behavior were also found to be moderately correlated with self-report measures of pro-environmental propensity. These findings support the suitability of the BAT for studying how people allocate their time between pro-environmental behavior and valued competing behaviors. More generally, they illustrate that behavior change interventions may benefit from targeting the behaviors that compete with societally beneficial behaviors.</p>