Potential energy surface for the O + CH3OCH2 reaction is calculated using the coupled cluster theory with single, double, and non-iterative triple substitutions [CCSD(T)] with a complete basis set extrapolation. It is revealed that the reaction of O with CH3OCH2 proceeds dominantly via an addition/elimination mechanism. Other minor mechanisms include direct hydrogen abstraction, which may play a significant role at high temperatures, and a high-barrier S(N)2 displacement. The initial adduct is the CH3OCH2O radical, which has many product channels via decomposition and isomerization. It is confirmed that beta-CH bond cleavage is the dominant product channel and all the remaining processes are of marginal significance. The rate coefficients for the barrierless association of O with CH3OCH2 are calculated to be in the range of (2.23-0.86) x 10(-10) cm3 molecule(-1) s(-1) with an apparently negative temperature dependence from 200-2000 K. For the H-atom production channel, the tunneling effect plays an important role and the barrier height is estimated to be 14.2 kcal mol(-1).