A reproducible route for the preparation of high-quality CdSe-ZnS-doped titania and zirconia waveguides is presented. The optical properties of the resultant composite materials are found to be sensitive to the semiconducting properties of the host matrix. Titania-based composites are seen to be inherently photounstable because of photoelectron injection into the bulk ma- trix and subsequent nanocrystal (NC) oxidation. In comparison, zirconia composites are significantly more robust with high photoluminescence (PL) retained for annealing temperatures up to 300 °C. Both titania and zirconia composite waveguides exhibit amplified stimulated emission (ASE); however only zirconia-based waveguides exhibit long-term photostability (loss of less than 30 % ASE intensity after more than 40 min continuous excitation). We conclude that the low electron affinity of zirco- nia and its inherent high refractive index makes it an ideal candidate for NC-based optical waveguides.