Ga0.47In0.53As and Al0.48In0.52As were grown lattice matched to InP substrates with a rotating substrate holder. The Ga, In, and Al beams were supplied by separate effusion cells and the uniformity of the resulting layers was evaluated with x‐ray rocking curves for different rotation speeds. Lateral variation of the lattice constant as small as 10−5per cm may be achieved with a rotation speed of 3 rpm. The full width at half‐maximum of the x‐ray spectrum from the epitaxial layer is comparable to that of the substrate indicating that there is practically no compositional grading.