The compositions and thicknesses of Y–Ba–Cu–O films radio frequency (rf) sputtered from a nonstoichiometric oxide target were determined as a function of deposition conditions. Variations in chamber pressure, rf power, and substrate position were observed to shift the as‐deposited cation composition along a single line in the Y–Ba–Cu ternary composition diagram. Deposition rates of up to 24 nm/min were achieved with good cation stoichiometry. Filmsdeposited on YSZ substrates at the optimized sputter conditions produced a zero resistance transition temperature of 88.7 K after a post deposition helium/oxygen heat treatment.Scanning electron microscopy(SEM) and x‐ray examination of the films revealed a strongly oriented large‐grain polycrystalline microstructure.