Studies by ellipsometry of the early stages of oxidation of the Be(0001) surface in the temperature range 30–600 °C have been made in conjunction with Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). An initial decrease in the ellipsometric parameter Ψ is taken to indicate incorporation of oxygen into the beryllium surface. The magnitude of the decrease in Ψ depends on temperature and is greatest around 100 °C. It is proposed that at the minimum in Ψ the surface consists of islands of BeO in an electron depleted Be layer; an effective medium approximation, assuming nearly free electron behavior for Be, can describe the experimental results with reasonable values of the parameters. After oxide coalescence, p(2×2)-BeO and ((3)1/2x(3)1/2)R30° -BeO LEED patterns are observed. They are unstable under an electron beam, but can be regenerated by short anneals at 500 °C. The ellipsometric parameter Δ is observed to be significantly different for the surface with and without this ordered structure. This change in Δ is not directly related to changes in the degree of order, but may be caused by electron beam enhanced decomposition of adsorbed gas. Ellipsometry results for oxygen on Ni(111) have also been obtained; these assist in the interpretation of the Be data.