We used x-ray photoemission and absorption spectroscopies to study the influence of thermal molecular oxygen exposure on the h-BN/Co(0001) and h-BN/Au/Co(0001) systems. The spectral analysis was supported by density functional theory calculations. It is shown that oxygen can intercalate h-BN on Co(0001) and also be embedded into its lattice, replacing the nitrogen atoms. Upon substitution, the structures containing one (BN ₂ O) and three (BO ₃ ) oxygen atoms in the boron atom environment are formed predominantly. In the case of gold-intercalated h-BN, only the (BN ₂ O) structures are formed; the long-lasting oxygen exposures lead to etching of the h-BN layer.