Single‐quantum‐well structures were grown by atmospheric pressure organometallic vapor‐phase epitaxy, with GaxIn1−xAs layers (0≤x≤1) coherently strained to match the lattice parameter of the InP barrier layers in the (100) growth plane. The strain effects on the band lineups were analyzed using the ‘‘model solid’’ theory of Van de Walle and Martin. The hydrostatic strain component for alloys withx≊1 is shown to be sufficient to marginally convert the type‐II lineups for the unstrained case to type I. The band lineups remain type I forx≊0. Considering the effect of strain, the ‖ (3)/(2) , (1)/(2) ⟩ valence subband becomes a slowly varying function ofx. Band offsets are predicted over the entire alloy composition and compared with the reported data. The photoluminescence (10 K) peak energies for the 100‐A˚ GaxIn1−xAs/InP single quantum wells compare quite favorably with the calculated strained band gap versusx. For nominal monolayer quantum wells, the peak energies are slightly above 1.1 eV over the entire alloy range. It is shown that forx>0.47, the LH1 and HH1 subbands cross at a smaller well width asxincreases. The ground‐state exciton is light hole‐like for larger values ofxandLz, and heavy hole‐like for smallerxandLz.