In this paper we report the successful synthesis of the cubic oxyanion containing perovskites, Ba(2)Sc(2-x)P(x)O(5+x) (x = 0.4, 0.5), with the samples analysed through a combination of X-ray diffraction, NMR, TGA, Raman spectroscopy and conductivity measurements. Conductivity measurements indicate a p-type contribution to the conductivity in oxidizing conditions at elevated temperatures, with evidence for proton conduction in wet atmospheres. For the latter, bulk conductivities of 5.9 × 10(-3) and 1.3 × 10(-3) S cm(-1) at 500 °C were obtained for x = 0.4 and 0.5 respectively, comparable to other perovskite proton conductors, while the stability towards CO(2) containing atmospheres was improved compared to BaCeO(3) based systems. Related Si doped systems have also been prepared, although in this case small Ba(2)SiO(4) impurities are observed. We also provide evidence to suggest that "undoped" Ba(2)Sc(2)O(5) contains carbonate groups, which accounts for its thermal instability.