Charge ordering and oxygen vacancy ordering are revealed in REBaMn2O6- (RE = Gd, Tb) oxides with perovskite-related structures. Electron diffraction and transmission electron microscopy results indicate a modulation of the crystal structure. The average oxidation state of Mn and the oxygen stoichiometry are determined by means of electron energy-loss spectroscopy, giving a REBaMn2O5.75 general formula. A 1:3 Mn4+:Mn3+ charge ordering model is confirmed by neutron powder diffraction, and oxygen vacancies-Mn3+ association is suggested by pair distribution function analysis. Direct imaging of the oxygen sublattice is obtained by phase image reconstruction. Location of the oxygen vacancies in the anion sublattice is achieved by analysis of the intensity of the averaged phase image. Both ionic conduction and multiferroic behavior are predicted from the crystal structures of these oxides.