Low-pressure glow discharges in He, Ne, or Ar gases containing small amounts of O2 can produce considerable dissociation of O2 molecules. High-lying metastable states in these noble gases play a predominant role in this process. Due to the difference in energies of metastable states of the noble gas atoms, there is a significant variation in the product states of O atoms created as a result of dissociation. Apparently, for He and Ne, superexcited O2 molecules are formed through collisions with high-lying metastable states of the noble gases. The superexcited O2 molecule could either autoionize to form an O2+ ion that subsequently captures an electron and dissociates or it could directly dissociate through some curve-crossing interactions yielding at least one atom in highly excited state. However, in the case of Ar, the formation of superexcited O2 may be possible through a prior creation of Ar2+ ion. We report some interesting observations on spectral emissions from O atoms in the three gas mixtures covering transition from 5d, 4d 3,5D, and 5s 3,5S, to 3p 3,5P levels and 4p and 3p 3,5P to 3s 3,5S levels. The emission from the b 4Σg−−a 4Πu system of O2+ ions is also reported. In general, populations of the above-stated O and O2+ levels are highest in the case of He–O2 mixture and lowest for the Ar–O2 mixture. However, the Ne–O2 mixture appears to strongly populate the 4p 5P levels, while the Ar–O2 mixture strongly populates the 3p 3P levels. The He–O2 mixture appears to be more efficient among the three gas mixtures considered in dissociating the O2 molecules.