Oxide ion conductors are technologically important materials with applications in solid oxide fuel cells, oxygen sensors /pumps and membranes for oxygen separation. Two types of oxide ion conductors are well-known, those with vacancy or interstitial mechanisms. Development of new materials relies on elucidating other, more complex mechanisms of ionic mobility in solids.We request 3 day of POLARIS/GEM beam time to perform neutron total scattering/PDF work on highly disordered oxide ion conductors Bi6WO12 and Bi28Re2O49, to determine their local structures, correlate them with properties, and establish the role of W and Re variable coordination in oxide ion mobility, which is strongly suggested by our extensive preliminary work. A broader significance of this work is that it will extend the range of oxide ion conductors in which this type of ionic mobility mechanism is significant.