Magneto-absorption experiments on a range on In1-xGaxAsyP1-y/InGaAsP multi-quantum well (MQW) structures, including both tensile and compressive strained wells, are presented. Estimates for the band offsets are made in a lattice matched and a strain-balanced structure, and a model to predict the band offsets as a function of strain in InGaAsP heterostructures is described.