Bi2Sr2Nb2GaO11.5 and Bi2Sr2Nb2AlO11.5, two new oxygen deficient Aurivillius-like Phases, were synthesized and their ionic conductivities were measured using ac impedance spectroscopy. Both oxygen ion conductors display discontinuities in the Ar-rhenius plot of their ionic conductivity. A phase transition, confirmed by differential thermal analysis, is consistent with an oxygen vacancy order-disorder transition. At 900-degrees-C the conductivities are 3.1 X 10(-2)S cm and 2.3 X 10(-2)S cm for Bi2Sr2Nb2GaO11.5 and Bi2Sr2Nb2AlO11.5, respectively.