Aqueous processing of 1- to 20-% v/v binary suspensions containing 0.50-μm α-Al2O3 and 0.71-μm m-ZrO2 was investigated in the presence and absence of AlCl3 from pH 2 to 12 using sedimentation, rheological, electrokinetic, and potentiometric techniques. Differential sedimentation of the oxide particulates leads to a nonuniform distribution of ZrO2 when colloidally stable slurries are used. However, processing under conditions that promote weak association of the oxides improves uniformity, with optimal conditions in the absence of AlCl3 being in the pH range 5 to 6. Thus, prefired microstructure depends on the pH at which processing occurs, behavior derived from the different, pH-dependent surface properties of the oxides. Pre-exposure of m-ZrO2 to AlCl3 in the pH range of 4 to 8 alters the final composite microstructure via adsorption of Al-species and renders the two solids more similar electrostatically, thereby reducing the forces responsible for the weak association and uniform distribution.