Fire is incontrovertibly an important disturbance in the North American tallgrass prairie, but little is known of the historic fire regime.  The crosstimbers forests of eastern Oklahoma are naturally bound by tallgrass prairie, and as such are periodically damaged at their edges by prairie fires.  Here we present a reconstructed fire regime from the fire-scar and tree-ring record of the Tallgrass Prairie Preserve, Osage County, Oklahoma.  At the preserve we collected 159 cross sections from uprooted oaks (primarily Quercus stellata and Quercus marilandica) for dendroecological analysis.  Our sample contained a record covering the past two and a half centuries with the oldest tree being some 277 years old.  Evidence of fire was present in every century, despite dramatic changes in the land use of the region.  We discuss the seasonality and frequency of fire in light of the need to manage natural areas for conservation.