Despite their motivational appeal to learners, innovative and technologically advanced computer simulation games targeting native English speakers frequently remain beyond the competence of ESL learners as independent didactic tools. Guided by Chapelle's (2001) criteria for determining CALL task appropriateness, this paper illustrates how the popular authentic simulation, The SIMs, can be adapted to enhance vocabulary learning through supporting materials. Adult ESL learners completed a five-week unit, experiencing different conditions of supplemental materials while completing tasks using The SIMs. The participants received mandatory supplemental materials in one condition, voluntary access to supplemental materials in the second, and no supplemental materials in the third. The results indicate a statistically significant increase in vocabulary acquisition for the first condition. Student feedback suggests the supplemental materials were beneficial for successful task completion. Thus, how authentic computer simulation tasks are structured and supported appears to have a considerable bearing on the appropriateness of the task.