We report optical characterization of the conduction band offset (CBO) between atomic-layer-deposited single crystal BeO and Si using internal photoemission (IPE) and internal multi-photon photoemission (IMPE), and of the valence band offset (VBO) using synchrotron x-ray photoelectron spectroscopy. The IPE/IMPE measurements indicate a CBO of 2.31 +/- 0.1 eV for 10 nm thick as-deposited oxides. For samples subjected to post-deposition anneal in N-2 at 600 degrees C and 900 degrees C, it increases to 2.54 +/- 0.1 eV and 2.61 +/- 0.1 eV, respectively. The VBO is stable at 4.14 +/- 0.2 eV for both as-deposited and annealed samples.