Transparent oxide materials have drawn considerable attention due to their unique electrical and optical properties, such as high electron mobility, and optical transparency. In particular, thin film transistors (TFTs) employing amorphous oxide semiconducting channels seem to constitute promising candidates for large-area electronics such as AMOLED displays because of the superior device characteristics over their polycrystalline counterparts or a-Si. Several amorphous oxide semiconductors (AOS), such as gallium indium zinc oxide (GIZO) and Indium zinc oxide (IZO), have been reported as alternative channel materials and fundamental electronic circuits have already been realised. Despite their attractive properties, however, AOS TFTs are usually realised using stringent and potentially costly manufacturing techniques. Here we demonstrate how spray pyrolysis, a simple and large-area-compatible deposition technique, can be used for the processing of high quality GIZO semiconducting channels. The GIZO semiconductors were spray coated onto thermal SiO2 substrates at temperatures in the range between 300 and 600 oC from soluble precursor solutions with varying the Ga, In, and Zn composition. At the optimum deposition temperature and composition, TFTs employing spray coated GIZO semiconducting channels exhibit excellent electron transport characteristics with negligible hysteresis operation, electron mobility in excess of 40 cm^2 V−1 s−1, and high on/off current ratio (10^6).