Methods of forming olyurethane foams that are the reaction product of at least one polyisocyanate and a polyol composition are provided. The polyol composition includes at least one natural oil based polyol and at least one poly(propylene oxide) polyol and is desirably free of non-natural oil based polyols made from alkylene oxide units, other than propylene oxide units. The natural oil based polyol is present in a quantity sufficient to increase the processing window for the foam relative to a foam made using the same process and the same components, absent the natural oil based polyol. As a result, the present foams can provide very open-cellular structures with the superior performance properties of a poly(propylene oxide) polyol-based foam.