The coadsorption of alkalis with CO and O on Cu(111) and Ni(111) was studied by vibrational measurements. Unexpectedly, we found an enhanced alkali oxidation rate for alkali + CO compared with alkali + O. Such finding was ascribed to the short-range alkali−CO interaction which lowers the barrier for CO dissociation and favors a giant alkali oxidation. Surprisingly, no alkali-O bond was formed for O/alkalis.