The effects of misfit strain on physical properties (lattice parameters, photoluminescence, and electron mobility) are discussed for In1−xGaxP epilayers with a constant thickness of around 0.75 &mgr;m grown by metalorganic molecular‐beam epitaxy on GaAs(001) substrates. The elastic accommodation of misfit strain is observed in the analysis of lattice parameters and energy‐band‐gap shift. Tensile strain is relaxed more easily than the compressive strain. Theoretical predictions of critical thickness for elastic‐strain accommodation and of energy‐band‐gap shift agree well with experimental results. The energy‐band‐gap shift and electron mobility are relatively insensitive to dislocations generated by relaxation of the misfit strain.