Coating compositions based on nonlinear, low molecular weight, polyester-based polyols having low viscosity and high solids content made by reacting a branched, polyhydric alcohol having at least three hydroxyl groups, such as trimethylolpropane; a glycol or diol; and a compound selected from the group consisting of a aliphatic or aromatic dicarboxylic acid, C₁-C₆ alkyl ester, anhydride, diacid halide, or mixtures thereof. The nonlinear, polyester-based polyols are quite effective in maintaining a high solids content while lowering viscosity when blended with other coating resins, such as acrylic resins, making the coating resins more effective in cured coatings by improving flexibility, impact resistance and hardness without adversely affecting appearance, solvent resistance, and/or accelerated weathering. This invention also relates to the process of coating a substrate with these coating compositions.