Ni-based alloy catalysts undergo dynamic structural changes during the dry reforming of methane (DRM), which impact their activity, stability, and resistance to coke formation. We systematically investigate the structural dynamics of La2O3-supported monometallic Ni, quaternary FeCoNiCu, and quinary FeCoNiCuMo catalysts, correlating these changes with catalyst properties and DRM performance. The quinary FeCoNiCuMo catalyst exhibits superior catalytic stability and coke resistance compared to the quaternary and monometallic Ni catalysts during 30 h on stream at 700 °C. Advanced dynamic characterizations reveal that multi-metallic alloying enhances coke oxidation by accelerating La2O3 ↔ La2O2CO3 redox cycling, increasing the concentration and mobility of active oxygen, and improving CO2 activation. These effects suppress CH4 decomposition by diluting Ni sites. This dual functionality establishes a self-sustaining redox cycle that balances coke formation and oxidation, accounting for the exceptional coke resistance observed in the high-entropy FeCoNiCuMo alloy catalyst. These findings provide fundamental insights into designing stable, coke-resistant DRM catalysts through controlled structural modulation and operando characterization under realistic conditions.