The high-temperature partitioning of Fe²⁺ and Mg between the two non-equivalent octahedral M1 and M2 sites in synthetic olivine (Fa₅₀) was studied by Mössbauer spectroscopy. Powder samples have been equilibrated in annealing experiments performed under reducing oxygen fugacity at temperatures between 500°C and 800°C followed by rapid quenching in order to prevent redistribution of cations. M-site ordering with Fe²⁺ preferring M1, Mg preferring M2 sites increases continuously with rising equilibrium temperature. K_D values increase from 1.21 at 500°C to 1.48 at 750°C. The results are consistent with both room temperature as well as in situ high temperature single crystal X-ray diffraction experiments of Heinemann et al. (2003a and b).