The interaction of CH₄ with a Pt(111)-(2×2)-O surface has been investigated by a supersonic molecular beam scattering technique. It was found that the CH₄ irradiation completely removes oxygen atoms from the surface via CH₄ oxidation reaction, CH₄ + O → CO + H₂, which is translationally activated. The oxidation probability of CH₄ on Pt(111)-(2×2)-O is found roughly of an order of magnitude greater than the initial dissociative chemisorption probability of CH₄ on Pt(111), especially under a low incident kinetic energy condition. From the angular intensity distribution and the time-of-flight distribution measurements of scattered CH₄, no significant difference in the collision dynamics of CH₄ both on Pt(111) and on Pt(111)-(2×2)-O is recognized.