Stationary points on the OH + CO --> H + CO2 potential energy surface are calculated using an extrapolated full coupled-cluster/complete basis set (FCC/CBS) method. The trans-HOCO intermediate is found to lie 30.10 kcal/mole below the OH + CO dissociation limit. For the forward reaction, the vibrationally adiabatic ground-state barrier height is predicted to be 1.03 kcal/mole. Finally, a many-body expansion potential energy surface for HOCO is obtained by fitting to the new ab initio results.