We report application of in-situ laser reflectometry in monitoring InAl1−xAs (0 ≤ x ≤1) epitaxial layers grown on a GaAs substrate by low pressure metal-organic chemical vapor deposition. Two different lasers were used simultaneously: One was a He-Ne laser operating at 0.6328 μm and the other was a diode laser operating at 1.53 μm. The two laser beams were incident on the growing layer at an angle of 71° from the surface normal, and the reflected beams were detected by Si and Ge photovoltaic detectors, respectively. Since the epitaxial layer of InxAl1−xAs (0 ≤ x ≤1) has a wide range of index of refraction, the reflected signals showed a variety of patterns. The optical constants of the InxAl1−xAs epitaxial layers were obtained for the entire range of composition.