The oxygen storage capacity (OSC) and its correlation with the activity for the CO oxidation reaction and the reducibility of the support material were investigated for four different metal oxide-supported Au catalysts with similar Au loading and Au particle sizes (Au/Al2O3 Au/TiO2 Au/ZnO Au/ZrO2) which were prepared by deposition of pre-formed Au colloids Temporal Analysis of Products (TAP) reactor measurements show that the OSC and the activity for CO oxidation measured under identical conditions differ significantly for these catalysts and are correlated with each other and with the reducibility of the respective support material pointing to a distinct support effect and a direct participation of the support in the reaction Activity measurements performed under ambient conditions show a similar trend of the activity as the TAP reactor measurements supporting that the conclusions drawn from the TAP reactor measurements are valid also under continuous reaction conditions Moreover the rapid formation and accumulation of carbon-containing surface species during reaction is demonstrated which can severely reduce the activity for CO oxidation Implications of these results on the CO oxidation mechanism over metal oxide-supported catalysts are discussed (C) 2010 Elsevier Inc All rights reserved