The large signal performance of electrostrictive materials, such as lead magnesium niobate-lead titanate (PMN-PT), is of critical importance to sonar transducer and actuator designers. However, obtaining these large signal parameters properly, particularly under compressive prestress, is an expensive and time-consuming enterprise. The complexity of these measurements, therefore, precludes them as a method for quickly and easily screening materials for their potential as high power materials. Traditionally, resonance measurements, which otherwise are relatively simple to perform, have been used for screening purposes, but they suffer from the drawback that the material parameters obtained are at the incorrect frequency and under no prestress. Furthermore, it was unclear what significance the results of resonance measurements for nonlinear materials such as electrostrictors had. It has recently been suggested that dc biased resonance measurements on electrostrictive ceramics would be an accurate predictor of the coupling factor and optimum bias point. In this paper, dc biased resonance measurements on three different PMN-PT formulations, with varying dielectric maximum temperatures, will be analyzed to determine which composition has the highest predicted coupling factor. This prediction will be compared with large signal quasistatic measurements conducted on NAVSEA Division Newport's SDECS (Stress-dependent Electromechanical Characterization System). The predictive ability of the resonance measurements will also be analyzed as a function of temperature normalized with respect to the dielectric maximum temperature.