The relative triple differential cross section for 100-eV electron-impact ionization of the three outer molecular orbitals of O2 has been studied in an asymmetric (e,2e) experiment. The angular distribution of low-energy ejected electrons was measured from 30° to 125° with respect to the incident beam direction for an incident electron scattering angle of 4° and ejected-electron energies of 3.5, 6.0, and 11.0 eV. The ionization of the outer 1πg orbital that leads to the formation of an O+2 ion in the X 2Πg state was observed to be accompanied by the ejection of a low energy electron 90° to the incident beam direction on the binary side. Binary results for the other two orbitals, 1πu and 3σg, to give the a 4Πu and b 4Σ+g states were similar to previous results for the analogous orbitals in N2 with ejection directions of 75° and 45° to the incident beam direction, respectively. In contrast to the N2 results, the recoil peak for all cases was found to be aligned approximately 180° to the momentum transfer direction. Possible mechanisms for the binary low-energy electron ejection at angles so far removed from the momentum transfer direction are discussed.