In the solid oxide fuel cell (SOFC) field, proton conducting perovskite electrolytes offer many potential benefits. However, an issue with these electrolytes is their stability at elevated temperatures in the presence of CO2. Recently we have reported enhanced oxide ion/proton conductivity in oxyanion (silicate, phosphate) doped Ba2In2O5, and in this paper we extend this work to examine the stability at elevated temperatures towards CO2. The results show improved CO2 stability compared to the undoped system, and moreover this can be further improved by co-doping on either the Ba site with La, or the In site with Zr. While this co-doping strategy does reduce the conductivity slightly, the greatly improved CO2 stability would suggest there is technological potential for these co-doped samples. (C) 2011 Elsevier B.V. All rights reserved.