A process for making cerium-containing oxide nanoparticles includes providing an aqueous reaction mixture containing a source of cerous ion and a source of one or more metal ions (M) other than cerium, a source of hydroxide ion, at least one monoether carboxylic acid nanoparticle stabilizer wherein the molar ratio of said monoether carboxylic acid nanoparticle stabilizers to total metal ions is greater than 0.2, and an oxidant. The cerous ion is oxidized to ceric ion, thereby forming a product dispersion of cerium-containing oxide nanoparticles containing one or more metal ions (M), Ce1-xMxO2-δ, wherein x has a value from about 0.001 to about 0.95 and δ has a value of about 0.0 to about 0.5.