The functional structure of the Oxygen Evolving Complex, the Mn4Ca cluster of Photosystem II, a critical component of natural photosynthesis, was analyzed at room temperature by EXAFS. An experimental improvement in the form of a spinning sample holder allowed us to efficiently counteract the severe X-ray damage sensitivity of Photosystem II to obtain high quality data subsequently used for a systematic evaluation of atomistic S1 state models. We investigated the accuracy of models collected by both conventional and femtosecond XRD at 1.9 and 1.95 angstrom resolution, respectively, as well as DFT-based models, to determine the structure most representative of experimental data. Additionally, room temperature EXAFS results do not show a visible reduction in the intensity of the k-space oscillations, supporting a rigid structure of the Mn4Ca cluster at room temperature.