InAlGaAs in combination with InP, InGaAs, and InAlAs is an attractive material for long wavelength applications. Reactive ion etching of InP/InAlGaAs/InGaAs heterostructures using CH4/H-2/Ar plasma is systematically investigated and optimization is obtained. The etching process is investigated as a function of radio-frequency power density and total pressure and its results are characterized in terms of etch rate, surface-roughness, and etch profile. Etch conditions for the smooth and reproducable etching of Al-containing heterostructures are reported. The quality of the results achieved is reflected by excellent quality epitaxial InP overgrowth.