In this chapter Perturbed Angular Correlation (PAC) experiments on binary oxides are described. These experiments provide local-scale fingerprints about the formation, identification, and lattice environment of defect complexes at the PAC probe site. The potential of the PAC observations in conjunction with ab initio calculations is shown. Measurements of the electric-field gradient at impurity sites using 111Cd and 181Ta probes are reviewed. Special attention is paid to oxides with the bixbyite structure. The case of In2O3 is particularly analyzed. Results obtained with HfO2, in form of coarse grain or nano particles, are described. The potential results that can be obtained from Density Functional Theory ab initio calculations in doped systems are shown describing the main results observed in many impurity-host systems.