We have studied the rate of oxygen diffusion through Sr2AlTaO6 (SAT), a buffer and dielectric layer used in high critical temperature superconducting (HTSC) structures. An epitaxial bilayer film of SAT on YBa2Cu3O7-δ (YBCO) was deposited onto an (001) oriented single crystal LaAlO3 substrate using the pulsed laser deposition technique. The rate of oxygen diffusion through the bilayer was investigated over the temperature range 415 to 675 °C by post deposition annealing individual sections of the bilayer in 1/3 atm of 18O enriched molecular oxygen gas. Secondary ion mass spectroscopy was used to depth profile 18O and 16O in each sample. Oxygen diffusion coefficients for SAT at 418, 510, 570 and 673 °C were determined to be roughly (0.93, 6.31, 26.6 and 75.3) × 10−16 cm2 s−1, respectively. Since these diffusion rates can limit oxygen intake into underlying YBCO films, SAT may be an inappropriate choice as a dielectric candidate for use in an HTSC multilayer device technology and will at best require development of suitable post annealing schemes to oxygenate underlying YBCO layers.