First-principles supercell calculations of oxygen vacancies in the Ba0.5Sr0.5Co1-yFeyO3-delta (BSCF) perovskites are presented. The density of states is determined for different iron content and oxygen vacancy concentrations, and the characteristic differences for Co and Fe are discussed. We analyze the dependences of the defect (oxygen vacancy) formation and migration energies on the Fe content and compare the calculated properties with those of related LaCoO3 and LaFeO3 perovskites. (C) 2010 Elsevier B.V. All rights reserved.