Iridium (Ir)-based materials are promising candidates for acidic oxygen evolution reaction (OER) but face challenges such as high cost and aggregation. In this study, we synthesized a low-Ir-content catalyst (1.47 at. %) via electrodeposition, where barium (Ba) doping introduces compressive strain to optimize Ir active sites while mitigating Ir aggregation into clusters or nanoparticles. Structural analyses, including X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), and extended X-ray absorption fine structure (EXAFS), confirm atomic-level dispersion of Ir and Ba, lattice contraction, and shortened Co-O bonds. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) reveal electron transfer from Ir to Co/Ba, elevating Ir’s oxidation state and enhancing OER activity. In 0.5 M H2SO4, the IrBa-Co3O4 catalyst achieves 10 mA cm-2 at an overpotential of 251 mV and operates stable for 100 hours, outperforming most reported spinel type catalysts. In-situ Raman spectroscopy and XANES attribute the improved kinetics to compressive-strain-induced octahedral Co-oxygen (Cooct-O) bond shortening and optimized Ir-O-Ba/Co coordination. This work demonstrates a strategy for designing cost-effective, durable acidic OER catalysts through synergistic doping and strain engineering.