The crystallography and texture of solid-state reactions have been studied using electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM). The crystallography of both the reaction interfaces and the grain boundaries plays an important role in the kinetics of the formation of the reaction products. The growth of the reaction products is dependent upon the transport of ions through the material, which is, in turn, affected by both the orientation of the reactants and by grain boundaries in the reactants and in the reaction products. In order to predict or control the behavior of the reactions, the crystallography of all the interfaces present in the reaction must be more fully understood. In the present study, MgIn2O4 was formed by the reaction between a single-crystal MgO substrate and a thin film of In2O3 with and without an applied electric field.