Gallium oxide is a wide band gap material with promising electronic and optical properties for potential use in gas sensing, catalytic, and optoelectronic device applications. Supported gallium oxide has been successfully investigated as a catalyst, especially in high temperature reactions such as dehydrogenation or oxydehydrogenation of light paraffins. However, the fundamental aspects of the surface catalytic properties, and especially the interaction of gallium with different supports are not well understood. In this study a series of supported gallium oxide catalysts were prepared by incipient wetness impregnation using silica (305 m²/g), alumina (160 m²/g), titania (85 m²/g), and magnesia (65 m²/g) as the supportes. Aqueous gallium nitrate solutions were used as precursors to achieve comparable loadings of 3.8-5.0 micromoles per square meter of the support. The catalytic properties were tested in CO oxidation and propane dehydrogenation reactions. In situ infrared spectroscopy investigation of the samples under flowing hydrogen (100 cc/min at 500^oC for 3 h) suggested the formation of gallium hydrides in all catalysts examined. The experimentally determined Ga-H frequencies were 2010 cm^-1 for Ga/SiO₂, 2005 cm^-1 for Ga/TiO₂, 1974 cm^-1 for Ga/Al₂O₃, and 1912 cm^-1 for Ga/MgO. In comparison with Ga/SiO₂ and Ga/MgO a strong intensity of the Ga-H bands was found in the case of Ga/Al₂O₃ and Ga/TiO₂. The ability to form surface gallium hydrides was more pronounced in the case of Ga/Al₂O₃ and Ga/TiO₂ catalysts. These results suggest a crucial role of the support in the formation of surface Ga-H species. The spectroscopic results were also correlated with the catalytic properties.