While transition metals are commonly used to catalyze the oxidation of small organic compounds, the mechanisms of these reactions are not yet completely understood. Silver surfaces are important industrial catalysts for the partial oxidation of ethylene to ethylene oxide and methane to methanol. While significant strides have been taken towards revealing the complex chemical pathways of oxidation reactions by silver surfaces, several aspects of the catalysis, particularly the different ways in which oxygen interacts with the silver surface have yet to be elucidated. This understanding is critical to determine the catalytically active oxygen-silver species that interacts with the reactants. It is also important to know how these active species change with reaction conditions, such as surface structure, surface temperature, and oxygen coverage, such that the conditions can be tuned to design the most effective catalysts. In the present study, density functional theory (DFT) was used to probe atomic-oxygen adsorption at the surface and subsurface of Ag(111) and Ag(110) surfaces. The main goal was to investigate the competition between surface and subsurface oxygen at different oxygen coverages, and study their participation in oxidation catalysis by silver surfaces. On the Ag(111) surface, it was found that adsorption energies for all surface and subsurface sites decreased with coverage; however, surface adsorption was compromised much more than subsurface adsorption. This difference causes a flip in preference from surface adsorption at low coverages to subsurface adsorption at high coverages. Calculated potential energy curves of oxygen moving from surface to subsurface on Ag(111) and Ag(110) show a complex interplay between adsorption energies and energy barriers that is sensitive to monolayer coverage. Results provide valuable insight into the competition between surface adsorption and subsurface adsorption of oxygen on the silver surface, the role of subsurface oxygen in catalysis by the silver surface, and the importance of charge transfer in the adsorption and dynamics of oxygen on the silver surface.