Here we present oxygen-nonstoichiometric transition metal oxides as highly prominent candidates to catalyze the industrially important oxidation reactions of hydrocarbons when hydrogen peroxide is employed as an environmentally benign oxidant. The proof-of-concept data are revealed for the complex cobalt oxide, YBaCo4O7+delta (0 < delta < 1.5), in the oxidation process of cyclohexene. In the 2-h reaction experiments YBaCo4O7+delta was found to be significantly more active (> 60 % conversion) than the commercial TiO2 catalyst (< 20 %) even though its surface area was less than one tenth of that of TiO2. In the 7-h experiments with YBaCo4O7+delta, 100 % conversion of cyclohexene was achieved. Immersion calorimetry measurements showed that the high catalytic activity may be ascribed to the exceptional ability of YBaCo4O7+delta to dissociate H2O2 and release active oxygen to the oxidation reaction.