BaFBr is usually contaminated with oxygen which influences the performance of this well known X-ray storage phosphor material. Oxygen is incorporated as a diamagnetic O^2- ion on F- sites with a nearby charge-compensating vacancy in the Br^- sublattice, as is known from the paramagnetic O^-_F and F(Br^-) centres created by room-temperature X-irradiation and studied in detail with electron paramagnetic resonance (EPR) techniques. It is shown that BaEBr:O^2-_F has a luminescence band excited at 4.95 eV, peaking at 2.43 eV with two radiative lifetimes of 0.2 ms and 1 ms, respectively. With luminescence-detected EPR (i.e. optically detected magnetic resonance (ODMR)), it is shown that the luminescence is due to an excited triplet state of an O^2-_F-Br^- vacancy pair. Time-resolved ODMR measurements reveal the same radiative lifetimes as seen in luminescence. No singlet emission was observed. The zero-field splitting can be explained assuming a F(Br^-)-O^-_F pair defect as the excited triplet state.