The frequency dependent dielectric properties of barium magnesium tantalate(BMT),Ba(Mg_(1/3)Ta(2/3))O_3 and barium zinc tantalate(BZT),Ba(Zn_(1/3)Ta_(2/3))O_3 synthesized by solid state reaction technique have been investigated at various temperatures by impedance spectroscopy.BMT and BZT possess cubic structure with lattice parameter a = 0.708 and 0.451 nm,respectively.The resonance peaks due to dielectric relaxation processes are observed in the loss tangent of these oxides.The relaxation in the samples is polydispersive in nature.The temperature dependence of dc conductivity,the most probable relaxation frequency(ω_m) obtained from tanδ vs logw plots and ω_m obtained from imaginary parts of the complex electrical modulus vs logw plots follow the Arrhenius behavior.According to these Arrhenius plots the activation energies of BMT and BZT are about 0.54 and 0.40 eV,respectively.Thus the results indicate that samples are semiconducting in nature.The frequency-dependent electrical data are analyzed in the framework of conductivity and electric modulus formalisms.Both these formalisms show qualitative similarities in relaxation time.Our study points that for complex perovskite oxides with general formula A(B’B“)O_3,the dielectric properties significantly depend on the atomic radii of both A and B type cations.BMT and BZT exhibit enhancement in dielectric property compared to their niobate counterparts.They may find several technological applications such as in capacitors,resonators and filters owing to their high dielectric constant and low loss tangent. The frequency dependent dielectric properties of barium magnesium tantalate (BMT), Ba (Mg 1/3 Ta 2/3) O 3 and barium zinc tantalate (BZT), Ba (Zn 1/3 Ta 2/3 )) O_3 synthesized by solid state reaction technique have been investigated at various temperatures by impedance spectroscopy. BMT and BZT possess cubic structure with lattice parameter a = 0.708 and 0.451 nm, respectively. The resonance peaks due to dielectric relaxation processes are observed in the loss tangent of these oxides. relaxation in the samples is polydispersive in nature. The temperature dependence of dc conductivity, the most probable relaxation frequency (ω_m) obtained from tan δ vs. logw plots and ω_m obtained from imaginary parts of the complex electrical modulus vs. logw plots follow the Arrhenius behavior. According to these Arrhenius plots the activation energies of BMT and BZT are about 0.54 and 0.40 eV, respectively. These results indicate that the samples are semiconducting in nature. The frequency-dependent electrical da ta are analyzed in the framework of conductivity and electric modulus formalisms. Both these formalisms show quite similarities in relaxation time. Our study points that for complex perovskite oxides with general formula A (B’B ”) O_3, the dielectric properties strongly depend on on the atomic radii of both A and B type cations.BMT and BZT exhibit enhancement in dielectric property compared to their niobate counterparts.They may find several technological applications such as in capacitors, resonators and filters due to their high dielectric constant and low loss tangent.