A detailed analysis of the reaction of CH3CCH2 and CH3CHCH with molecular oxygen is presented. The C3H5O2 potential energy surface was characterized using a combination of electronic structure methods. The majority of the stationary points on the PES was determined at the CCSD(T)-F12a/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ level of theory, with the remaining transition states computed using multireference methods. Microcanonical rate theory and the master equation are used to determine the temperature- and pressure-dependent rate coefficients for each reaction channel. The main product channels are CH2O + CH3CO for CH3CCH2 and CH3CHO + CHO for CH3CHCH. The rate constants for these two reactions at 1 atm are k = 9.03 x 10(22) x T-3.21 x exp(-2162/T) and 1.50 x 10(19) x T-2.10 x exp(-1260/T) cm(-3) mol(-1) s(-1), respectively. In contrast to C2H3 + O-2, the methyl-vinyl + O-2 reactions remain chain propagating, even at high temperatures. The new rate coefficients were implemented in a detailed mechanism taken from the literature. These changes have a modest effect on the ignition delay time and laminar flame speeds for propene combustion.