The current state of art for corrosion protection of steel bridges involves a three-coat system typically consisting of a zinc-rich primer, an intermediate coat, and a top coat. Replacing a three-coat system with fewer coats without sacrificing corrosion resistance can lead to savings in production cost and improved productivity in the steel shops. Two-coat systems evaluated in a previous Federal Highway Administration study performed on par with the widely established well-performing zinc-rich three-coat systems. In this in-house one-coat study, commercially available coating materials that can be applied as one-coat systems to new steel bridges were evaluated. Eight one-coat systems and two controls, a three-coat and a two-coat system, were chosen, and their performance was evaluated using accelerated laboratory testing (ALT) and two outdoor exposure conditions, natural weathering (NW) and natural weathering with salt spray (NWS). ALT (6,840 h) and the two outdoor exposure conditions (NW and NWS), both 18 months, were performed at the Coatings and Corrosion Laboratory at the Turner-Fairbank Highway Research Center in McLean, VA, while another outdoor exposure was performed at a marine exposure site for 24 months in Sea Isle City, NJ. The purpose of this study was to evaluate the performance ranking of various one-coat test systems.