Low‐threshold arrays of GaAs/AlGaAs patterned quantum well semiconductor lasers were grown by molecular beam epitaxy on periodically corrugated substrates. Uncoated arrays of ∼14 lasers operated with threshold curents of 3.6 mA per laser and emitted up to 375 mW from a single facet under pulsed conditions. The array lasers were not phase locked because of the tight optical confinement in each array channel. A red shift of 300 A˚ (55 meV) was observed in the emission wavelength of the patterned array compared to that of nonpatterned lasers made on the same substrate. The red shift results from migration effects in the growth on the nonplanar surface, which leads to thicker quantum well active regions at the array channels. This effect illustrates the usefulness of the growth of quantum well heterostructures on nonplanar substrates for lateral band‐gap engineering.