High-entropy materials (HEMs) have attracted extensive attention in the field of electrochemical catalysis due to their unique properties. However, the preparation of high-entropy catalysts typically relies on high-temperature, energy-intensive, and time-consuming synthesis methods due to their compositional complexity. In this study, a facile low-temperature electrochemical reconstruction approach is adopted to synthesize Ag-decorated septenary Co-Cu-Fe-Mo-Zn-Ag-Ru high-entropy (oxy)hydroxide electrocatalysts for oxygen evolution reaction (OER). By introducing Ag and Ru elements and implanting Ag nanoparticles to co-regulate the electronic structure of the catalysts, the as-prepared catalyst achieves remarkable OER performance with a low overpotential of 298 mV at 100 mA/cm² and a small Tafel slope of 30.1 mV/dec in 1 mol/L KOH. This work offers a valuable strategy for developing high-performance high-entropy OER electrocatalysts.