We introduce a new technique for imaging oxygen concns. in fuel/air mixts. that takes advantage of the different responses of toluene and 3-pentanone to collisional quenching by mol. oxygen. Since laser-induced fluorescence signals from both tracers upon excitation at 248 nm are spectrally well sepd., simultaneous detection is possible. The technique is first applied to instantaneous imaging in turbulent mixing processes of interacting seeded air and nitrogen flows.