The synthesis, structure, and dielectric properties of the so-called M-phase solid solutions in the Li2O-Ta2O5-TiO2 system were investigated. Although the range of stability of the tantalate phases is more limited compared with their niobate counterparts, they have identical structures based on inter-growths of LiTaO3-type blocks separated by corundum type layers. The dielectric constants of the tantalate M-phases range from 68 to 52 and they all exhibit a negative temperature coefficient of capacitance. The temperature coefficient of the resonant frequency measured in the microwave region can be tuned to zero, and the system shows quite good quality factors with the highest value reaching a Q x f = 10500 at 6.7 GHz.