The coarsening kinetics of a magnesia‐partially‐stabilized zirconia with and without ternary additions of calcia, titania, or yttria at the 2 mol% level have been studied as a function of aging time at 1420°C. Addition of titania was found to markedly increase the coarsening rate and it is thought that this is due to a higher precipitate volume fraction in this system. Both calcia and yttria decreased the coarsening kinetics by a similar amount, probably due to both lower precipitate volume fractions and lower interdiffusion coefficients. The precipitate “transformability” was found to vary among the four systems examined, with calcia and yttria acting to stabilize tetragonal precipitates to larger sizes; titania was found to act as a destabilizer. Coherency stresses are important in determining the precipitate morphology and distribution in these alloys but we were unable to ascertain what effect these stresses had on the coarsening rates of the differen