A catalyst operates by stabilizing reaction intermediates through surface adsorption. In the oxygen evolution reaction (OER), the surface electro-adsorptions stabilize the oxygen-containing intermediates as the catalyst breaks and connects the oxygen-hydrogen and oxygen-oxygen bonds. While this concept has led to many new OER-catalyst discoveries, the experimental relationship between the electro-adsorption energetics and the OER kinetics remains to be established. We present our measurements of the electro-adsorption energetics on IrO₂(110) and RuO₂(110) epitaxially grown on TiO₂(110) substrates. The high quality of the oxide films grown using molecular-beam epitaxy affords the ability to extract the oxygen electro-adsorption energetics, consequently enabling us to quantify the relationship between the electro-adsorption and the OER. Putting together the adsorption energetics allows us to examine the validity of the scaling relation, an idea that the surface binding energy can be approximated by the first bond to the surface. Our measurement experimentally supports the scaling relation concept, thereby suggesting that the volcano relationship, the consequence of the scaling relation, could be valid on average. However, we also note some deviations, which do not impact the overall trend of the scaling relation but are sufficiently present that they could lead to superior OER catalysts if these deviations can be successfully understood and utilized.