Recent developments in the antifouling properties of Self-Assembled Monolayers (SAMs) have largely focused on increasing the enthalpic association of a hydration layer along the interface of those surfaces with water. However, an entropic penalty due to chain restriction also disfavors biomolecule-surface adsorption. To isolate the effect of this entropic penalty amid changing packing densities, molecular dynamics simulations of explicitly solvated systems of lysozyme and seven monomer length oligo (ethylene glycol) (OEG) SAMs were performed. SAM surfaces were constructed at 100%, 74%, and 53% of a maximum packing (MP) density of 4.97 Å interchain spacing and the effect of chain flexibility was isolated by selectively freezing chain monomers. The rate of protein adsorption as well as the conformation and orientation of the protein upon adsorption were examined. It was found that chain spacing was a strong determinant in adsorption properties while chain flexibility played a secondary role. Of the three packing densities, 74% of MP was the most antifouling with increased antifouling behavior at moderate chain flexibility, i.e. two to four free monomer groups.