The first measurements of electroabsorption in AlGaAs/GaAs multiple quantum wells grown on transparent GaP substrates are reported. High quality quantum well materials with sharp, well defined excitonic resonances are grown by employing a GaAsP intermediate layer between the quantum wells and the substrate. Good surface morphology and abrupt interfaces have been achieved with etch pit densities of 4×105cm−2. A 7.5‐meV shift of the absorption edge to lower energies is observed for field strengths of 8×104V/cm. These structures are well suited for photonic switch array fabrication.