Osmium-based oxides show a wide range of interesting properties due to the variety of oxidation states osmium can adopt combined with 5d electrons displaying strong spin-orbit coupling. We plan to investigate the ambient- and low-temperature structures of Sr6Os6O19 and Bi3Os3O11 to understand the electronic structure and magnetism in these compounds. Both compounds have cubic KSbO3-type structures with osmium-osmium bonds and both show anomalies in magnetic susceptibility at low temperature. Special attention will be given to these osmium-osmium bonds in our analysis as well as the oxygen coordination of the Os ions, both of which are crucial for understanding the magnetism and electronic properties of these materials.