Ternary compositions based on Bi(B′B″)O3–PbTiO3-type compounds have been investigated for high-temperature piezoelectric applications. Compositions in the ternary were chosen to be near the binary morphotropic phase boundary (MPB) composition of BiScO3–PbTiO3 (BS–PT). Ternary compositions in (100−x−y)BiScO3–(x)Bi(Zr0.5Zn0.5)O3–(y)PbTiO3 [(100−x−y)BS–xBZZ–yPT] have been investigated with x ≤ 7.5. For compositions with x > 10, the Curie temperature (TC) decreased below 400°C. Dielectric, piezoelectric, and electromechanical properties were characterized as a function of temperature, frequency, and electric field. Small additions of BZZ were shown to increase the electromechanical properties with only a small loss in TC. The electromechanical properties were temperature stable up to the depoling temperature. The most promising composition exhibited a TC of 430°C, piezoelectric coefficient (d33) of 520 pC/N, and a planar coupling factor (kp) of 0.45 that remained unchanged up to depoling temperature at 385°C.