This proposal requests 3 days on Maps to investigate the nature of local structure and proton sites in the proton conducting brownmillerite system Ba2In1.85M0.15O6H2 (M = In, Sc, Y, Ga). Our current work on this system focuses on investigations of local structural details, using Raman and IR spectroscopy. A key result from our most recent studies is that the nature of proton sites as well as the underlaying brownmillerite structure is locally affected by both hydration and the modifying cation (M). However, the nature of these local structural differences remain to be elucidated. For this reason, we propose to perform a systematic INS study, which will complement the Raman/IR spectra already collected and, when coupled to DFT calculations, will allow for an unambiguous assignment of the INS/Raman/IR bands, which implies that unique information about structural details can be obtained.