The utilization of high temperature solutions has been very effective for the growth of oxide single crystals containing virtually all elements in the periodic table with a wide range of oxidation states.  Oxide crystals have been grown from many different high temperature solutions, including alkali and alkaline earth carbonates, halides, peroxides, super oxides, and hydroxides.  Of these diverse solvent systems, the hydroxide melts have proven to be the most advantageous for obtaining crystals containing elements in unusually high oxidation states.  Our group has been concentrating on the use of such melts to incorporate members of the platinum group metals into oxide structures.  To that end, we have synthesized new rare-earth ruthenates and rare-earth osmates from hydroxide fluxes.  As a function of rare-earth size, we obtain double perovskites -- RE₂NaMO₆ (M = Ru, Os; RE = La, Pr, Nd), defect fluorite oxides -- RE₃MO₇ (M = Ru, Os; RE = Sm, Eu, Gd).  The structures, including structure transitions, and magnetic properties are presented.