Results are presented on the optimization of oxygen content and order in YSr 2 Cu 2 . 7 5 Mo 0 . 2 5 O z (YSCMO) thin films. It is shown that due to the high vapor pressure of the chain oxygen of this doped cuprate, optimal oxygenation cannot be achieved through annealing in O 2 at 1 atm. Optimization of oxygen content can be accomplished globally by ozone anneals at 1 atm, and locally, in thin film microbridges, by electromigration of chain oxygen vacancies out of the microbridges. Both techniques lead to a maximal T c of 75 K, substantially higher than has been previously achieved in this material. The strong correlation between the enhancement in superconducting and normal state properties, and improvements in oxygen content has been verified by micro-Raman spectroscopy. These results suggest that YSr 2 Cu 3 - x M x O z materials in general may be substantially under-oxidized if annealed in O 2 at less than extremely high pressure, or without some other means that can overcome a comparatively high chain-oxygen vapor pressure at typical annealing temperatures. This could affect the interpretation of previous experiments with doped cuprate superconductors.