Site engineering has been employed to modulate the piezoelectric activity of high temperature (1 − x)Bi_1.05Fe_1−ySc_yO₃–xBaTiO₃ lead-free ceramics fabricated by a conventional solid-state method together with a quenching technique. The effects of x and y content on the phase structure, microstructure, and electrical properties have been investigated in detail. A wide rhombohedral (R) to pseudo-cubic (C) phase boundary was formed in the ceramics with x = 0.30 and 0 ≤ y ≤ 0.07, thus leading to enhanced piezoelectricity (d₃₃ = 120–180 pC N⁻¹), ferroelectricity (P_r = 19–22 μC cm⁻²) and a high Curie temperature (T_C = 478–520 °C). In addition, the influence of different element substitutions for Fe³⁺ on phase structure and electrical behavior was also investigated. Improved piezoelectricity (d₃₃ = 160–180 pC N⁻¹) and saturated P–E loops can be simultaneously achieved in the ceramics with A = Sc, Ga, and Al due to the R–C phase boundary. As a result, site engineering may be an efficient way to modulate the piezoelectricity of BiFeO₃–BaTiO₃ lead-free ceramics.