The experimental results of the rapid thermal oxidation in the initial oxidation regime of molecular beam epitaxy grown GeSi strained layers are reported. It is shown that the dry oxidation rate of GeSi is the same as that of Si at different temperatures. After a very short initial time (∼10 s), the oxide thickness appears to be a linear function of time, which suggests that the kinetics of oxide growth during dry oxidation is limited by surface reaction controlled mechanisms. Further, the oxidation rate in the thin oxide regime is not affected by the Ge content up to 20% in the GeSi strained layer for dry oxidation. Using secondary‐ion mass spectrometry, it is found that Ge is completely rejected out of the SiO2layer which is formed during oxidation, and a Ge‐rich layer is formed at the SiO2/GeSi interface. A significant amount of Ge is found to diffuse into the underlying GeSi layer during the growth of thin oxide films.