We report the first high quality optical waveguides (loss <1 dB/cm) on alumina and beryllium oxide substrates. The tunability of the polymer guiding layer refractive index is provided through a recently developed wet processing technique. This procedure changes the waveguide propagation loss from larger than 40 dB/cm to less than 1 dB/cm. Since alumina (Al2O3) and beryllium oxide (BeO) are the major substrates for hybrid mode microwave integrated circuits (HMMICs), realization of such waveguides is useful for optical interconnection and signal processing for HMMIC.