Spectra were recorded in the H-F stretching fundamental region for O-2-HF and in the D-F region for O-2-DF, using a laser difference-frequency spectrometer coupled to a slit-nozzle expansion. By varying the ratio of oxygen to carrier gas, beam temperatures ranging from 5 to 16 K were obtained. One standard uncertainty for the relative frequency position of unblended lines is 0.0001 cm(-1). Each spectrum was visually subdivided into a stronger (cold) spectrum and a weaker (hot) spectrum. Lines in the cold spectrum were fit to nearly experimental error, using a rotational Hamiltonian for open-shell complexes taken from the literature. For O-2-DF, 21 rotational and spin-rotational parameters (10 each for the upper and lower state plus the band origin) were used to fit 86 transitions to a standard deviation of 0.0002 cm(-1). For O-2-HF, 23 rotational and spin-rotational parameters were used to fit 83 transitions to a standard deviation of 0.0003 cm(-1). The slightly poorer quality of the fit for O-2-HF than for O-2-DF is probably related to the somewhat larger vibrational amplitudes expected for the van der Waals motions in the protonated species. In spite of strenuous efforts, a simultaneous global fit to measurement error of the eight cold-spectrum branches and fourteen hot-spectrum branches could not be achieved, suggesting some improvement in the model used to derive the fitting Hamiltonian may be necessary.