The oxygen pressure P(O2) during growth of strontium titanate (SrTiO3) films on single crystals of (1102BAR) oriented sapphire (Al2O3) substrates significantly influenced the film orientations. The films were deposited using a pulsed laser (248 nm) deposition process in which the SrTiO3 films were deposited at a P(O2) of either 40 or 200 mTorr, and the YBa2Cu3O7-x (YBCO) films were always deposited at 200 mTorr of oxygen. We found that growth at 40 mTorr induced the (110) SrTiO3 orientation to predominate, while increasing the P(O2) to 200 mTorr favored the (100) orientation. YBCO films deposited on these barrier layers were (013) and (001) oriented respectively; these were the orientations that minimized lattice mismatch at the YBCO/SrTiO3 interface.