Disclosed are mixtures of oxyalkylene bridged bis- and tris-phosphite esters of formulae I and II where R is hydrogen or methyl, n and n′ are independently an integer from 1 to 45 and R1, R2 and R3 are each independently hydrogen, straight or branched chain alkyl of 1 to 12 carbon atoms, phenylalkyl of 7 to 9 carbon atoms, phenylalkyl of 7 to 9 carbon atoms substituted on the phenyl ring by one to three straight or branched chain alkyl of 1 to 12 carbon atoms or R1, R2 and R3 are each independently —(CH2)k—COOR4 where k is 0, 1 or 2 and R4 is hydrogen or straight or branched chain alkyl of 1 to 20 carbon atoms. The mixtures of formula I and II are liquid at ambient conditions and are effective stabilizers for polyolefins.