To improve the stability of porous Si (PS) prepared by electrochemical etching, we make use of rapid-thermal oxidation (RTO). During RTO processing, the hydride coverage of the internal surfaces of the pores is replaced by a high-quality oxide while retaining nm-sized Si grains. With increasing process temperature T(ox) the luminescence is first quenched. It is recovered with comparable intensity for T(ox) greater-than-or-equal-to 700-degrees-C.