An electrorheological fluid is modeled as a concentrated suspension of hard spheres with aligned field-induced electric dipole moments. The presence of dipole moments causes clustering of the particles into an anisotropic suspension characterized by a particle probability distribution function. The elastic shear modulus and the dynamic viscosity are calculated from a perturbation to the particle distribution as a result of a small amplitude, high frequency, oscillatory flow. The high frequency elastic shear modulus and the dynamic viscosity are shown as a function of particle concentration and electric dipole strength. Both the modulus and the viscosity increase strongly with particle concentration. Dynamic viscosity is insensitive to dipole strength, but elastic shear modulus increases strongly with dipole strength indicating the relative importance of the particle distribution to elastic properties. The results of these calculations provide insight into the relationship between the macroscopic properties of an electrorheological fluid and microscopic structural changes.