Educational multi-user virtual environments (MUVEs) have been shown to be effective platforms for situated science inquiry curricula. While researchers find MUVEs to be supportive of collaborative scientific inquiry processes, the complex mix of multi-modal messages present in MUVEs can lead to cognitive overload, with learners unable to effectively process the rich information encountered in virtual space. In this study, we investigated the effect of communication modality on cognitive load and science inquiry learning in students completing a science inquiry curriculum in an educational MUVE. Seventy-eight undergraduate education majors from a large southwestern university participated in this control-treatment study. Significant positive results were found for reducing cognitive load for participants communicating through voice-based chat, although this reduction was not found to influence learning outcomes. We conclude that use of voice-based communication can successfully reduce cognitive load in MUVE-based inquiry curricula. (Contains 4 tables and 3 figures.)