Oxides of the type LaBaZnTaO6 and LaSrZnNbO6 have been synthesized by the solid-state method at 1100 degreesC. Ba2Zn0.5Ti0.5TaO6 was synthesized by the molten salt method (using NaCl-KCl as flux), the solid-state method yielding a biphasic mixture of BaTiO3 and BaZn1/3Ta2/3O3. LaBaZnTaO6 and LaSrZnNbO6 were found to crystallize in an ordered (cubic) double perovskite structure in the Fm (3) over barm space group with a = 8.0867(8) and 8.001(1) Angstrom, respectively. Ba2Zn0.5Ti0.5TaO6 crystallizes in the disordered cubic perovskite structure with a = 4.054(1) Angstrom. These oxides have very low dielectric losses in the region of 0.0005 to 0.003 (500 kHz). The dielectric constants of LaBaZnTaO6 and LaSrZnNbO6 are low (13 and 10, respectively) while Ba2Zn0.5Ti0.5TaO6 has a high dielectric constant of 36 at 500 kHz.