Computer simulation techniques have been used to model cubic CeO2-ZrO2 solid solutions in the whole composition range. Aspects related with the oxygen storage capacity of these materials are emphasized. The energetics of the Ce4+/Ce3+ bulk reduction reaction as well as the activation energy for oxygen migration in the lattice are investigated and compared with the corresponding quantities in pure CeO2. It is found that even small additions of ZrO2 decrease the bulk reduction energy of Ce4+ to values comparable to those reported for surface reduction in pure CeO2. Activation energy calculations indicate an almost monotonic increase of oxygen mobility with increasing zirconia content.