We have studied the rate of oxygen diffusion through ytterbium oxide (Yb2O$3), a buffer and dielectric layer used in high critical temperature superconducting (HTSC) structures. An epitaxial bilayer film of Yb2O3 on YBa2Cu$3)O7-(delta ) (YBCO) was deposited onto an (001) oriented single crystal MgO substrate using the pulsed laser deposition technique. The rate of oxygen diffusion through the bilayer was investigated from 365 to 655 degree(s)C by post deposition annealing individual section of the bilayer in 0.5 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 Yb2O3 at 365, 465, 555 and 655 degree(s)C were determined to be roughly (6, 16, 360, and 200) X 10-1, respectively. For temperatures greater than about 500 degree(s)C, these diffusion rates can limit oxygen intake into underlying YBCO films; therefore, HTSC multilayer devices that utilize Yb2O3 as a dielectric layer may require longer annealing cycles in order to fully oxygenate each underlying HTSC layer.