A strong de electric field dependence of the dielectric permittivity makes perovskite ferroelectrics promising materials for tunable microwave devices like phase shifters, tunable resonators, tunable filters etc. Dielectric loss is a crucial parameter for these applications. It has been recently realized that the so-called quasi-Debye loss mechanism related to local or global violation of central symmetry of materials plays a important;.,I the total balance of microwave loss. This mechanism controls the increasing dc field dependence of microwave loss in high-quality ferroelectric materials. The present paper reports on modeling oil the quasi-Debye loss mechanisms in SrTiO3 and KTaO3 systems. it is concluded that the contribution of this mechanisms is large enough to affect the performance of ferroelectric-based tunable microwave devises.