The effects of CuO or NiO addition on the sintering temperature and electrical properties of 0.92(K0.47Na0.47Li0.06)NbO3-0.07BaZrO3-0.01(Bi0.5Na0.5)TiO3 ceramics with a temperature-stable morphotropic phase boundary were investigated. The ceramics without any additives and those with NiO exhibited a tetragonal phase. The ceramics with CuO exhibited the coexisting orthorhombic and tetragonal phases. The sintering temperature was reduced by the addition of NiO or CuO. NiO addition was also effective for broadening the range of the sintering temperature window. The d33, radial-mode electromechanical coupling factor, and remanent polarization of the ceramics with NiO were 238 pC/N, 0.39, and 14 µC/cm2, respectively; moreover, the measured values of the ceramics with CuO were all lower than those of the ceramics with NiO. The results suggest that NiO acted as a sintering aid among grains, and the sintering temperature window was consequently broadened. In the case of CuO addition, Cu ions replaced the A- and B-sites of the ceramics, and such replacement reduced the tetragonality. As a result, the electrical properties of the ceramics with CuO were lower than those of the ceramics with NiO.