Transient oxidation of C4 hydrocarbons was studied using the pulse technique over a two-phase catalyst (MnMoO4/MoO3) and its pure phase constituents, MoO3 and MnMoO4. The role of lattice and gas-phase oxygen was examined in the oxidation of 1-butene, 1,3-butadiene, furan, and maleic anhydride using oxygen-free and oxygen-abundant mixtures. The results confirmed the synergy previously observed between the two phases of the MnMoO4/MoO3 catalyst and suggested a catalytic job distribution where oxygen from the MoO3 lattice was incorporated to the hydro-carbon molecule and the MoO3 sites were regenerated through an oxygen spillover mechanism from the MnMoO4 phase.