Polyether polyols and polyurethane foams are stabilized by including therein a liquid stabilizer composition of (a) 2,6-di-tert-butyl-4-sec-butylphenol, (b) a reaction product of diisobutylene, styrene and diphenylamine and (c) phenothiazine or C.sub.9-26 -alkyl substituted phenothiazine and wherein the ratio of the phenol to the reaction product is about 1:5 to 5:1 and the ratio of the mixture of components (a) and (b) to the phenothiazine compound is about 5.0:0.1 to 4.0:1.0. The stabilizer composition may further contain trihydrocarbyl phosphite to stabilize the color of same.