A new class of complex perovskite oxides Ba(2)REZrO(6-x) (RE = Pr, Nd, Sm and Gd) have been synthesised and sintered as single phase materials with high sintered density and stability by solid state reaction method. The structure of Ba(2)REZrO(6-x) was studied by X-ray diffraction technique and all of them were found to be isostructural and have a cubic perovskite structure. No chemical reaction was observed between Ba(2)REZrO(6-x) and YBa2Cu3O7-delta even after annealing a 1:1 volume mixture at 950 degrees C for 20 h. The dielectric constant and loss factor of these materials are in a range suitable for their use as substrates for YBa2Cu3O7-delta superconductors. Ba(2)REZrO(6-x) melts congruently and could be grown as single crystals from melt.