Low-voltage operation has long been a beneficial characteristic of electrolyte-gated organic transistors (EGOTs) because of the high capacitance of the electrolyte dielectric layer. Operating below 3 V, several reported EGOTs have effective mobilities above 1 cm2V−1s−1 based on the recently introduced reliability factor for organic field-effect transistors (OFETs). In this study, we report on the influence of gate voltage operation on the effective mobilities of EGOTs using poly(3-hexylthiophene) (P3HT) semiconductor and electrolyte dielectric operating at different gate voltages of −1, −1.5, and −2 V. Average field-effect mobilities (μFET) of 2.35 ± 0.41 (2.39 ± 0.27), 3.74 ± 0.33 (2.95 ± 0.32), and 3.30 ± 0.44 (2.81 ± 0.38) cm2 V−1 s−1 are measured in the saturation (linear) regimes for devices operating at −1, −1.5 and −2 V, respectively. With a reliability factor of 74.9 ± 2.8% (86.2 ± 2.2%) in the saturation (linear) regime, devices at −1.5 V measured the highest average effective mobility (μeff) of 2.79 ± 0.22 (2.54 ± 0.29) cm2 V−1 s−1 in the saturation (linear) regime due to efficient charge transport with minimal charge scattering. Our results highlight fundamental optimization techniques helpful for achieving optimal effects.