The demise of mammoths, during the terminal Pleistocene extinction event, thrust bison into a role as both the keystone herbivore of the Great Plains grasslands and the most important prey resource for the established human populations. Since the end of the Pleistocene, the genus Bison underwent significant anatomical and behavioral changes. This study examines opal phytoliths embedded in dental calculus of prehistoric bison specimens as a proxy for reconstructing environmental context of anatomical and behavioral changes underwent by the Great Plains bison since the terminal Pleistocene. The strategy includes comparing prehistoric phytolith assemblages with those of modern bison in various types of grasslands. The paleo-bison examined were sourced from the Beaver River Bison Hunting Complex, the Ravenscroft II Bison Kill Site and the Folsom Site, in Oklahoma and New Mexico. This research shows that phytolith analysis is a viable method of adding additional data to other studies on bison paleo-ecology. The phytolith counts obtained indicate a significant climatic and potential ecological difference between the ancient bison and the modern references, which were analyzed.