The reactions of niobium and tantalum monoxides and dioxides with methane have been investigated using matrix isolation infrared spectroscopic and theoretical calculations. The niobium and tantalum oxide molecules were prepared by laser evaporation of Nb2O5 and Ta2O5 bulk targets. The niobium, monoxide molecule interacted with methane to form the ONb(CH4) complex, which was predicted to have C-3 nu, symmetry with the metal atom coordinated to three hydrogen atoms of the methane molecule. The ONb(CH4) complex rearranged to the CH3Nb(O)H isomer upon 300 nm < lambda < 580 nm irradiation. The analogous OTa(CH4) complex was not observed, but the CH3Ta(O)H molecule was produced upon UV irradiation. The niobium and tantalum dioxide molecules reacted with methane to form the O2Nb(CH4) and O2Ta(CH4) complexes with C, symmetry, which underwent photochemical rearrangement to the CH3Nb(O)OH and CH3Ta(O)OH isomers upon ultraviolet irradiation.