A new method for the growth of solid-solution thin films has been developed in which a pre-determined ratio of the components can be deposited by the controlled use of a single rotating target. This variable compositional control is achieved by altering the radial position of either the target, which incorporates wedge-shaped segments of the solid-solution components, or of the laser beam. The method was used to grow films of the solid solution KTa1-xNbxO3 for which the predicted and measured values of the ferroelectric transition temperature far selected Ta/Nb ratios were in excellent agreement. This approach is generally applicable to solid-solution systems and is not restricted to ferroelectric oxides.