The compounds are trialkylsubstituted hydroxyphenylalkanephosphinates and phosphonates having the formula ##STR1## wherein R, R.sup.1 and R.sup.2 are independently lower alkyl or cycloalkyl groups, R.sup.3 is alkyl, alkyl substituted with one halogen atom, phenyl, phenyl substituted with alkyl groups, alkoxy, alkoxy substituted with one halogen groups, phenoxy, phenoxy substituted with alkyl groups, alkylthioethoxy, alkyloxalkylenoxy, R.sup.4 is alkyl, alkyl substituted with one halogen atom, cycloalkyl, phenyl, phenyl substituted with alkyl groups, alkylthioethyl, thiobisalkylene, alkylene, polyvalent cyclic or acyclic hydrocarbon radical, A is lower alkylene and n is 1 to 4.These compounds are usually prepared by reacting the trialkylsubstituted hydroxybenzyl or hydroxyphenylalkyl halide with the appropriate tralkyl or triaryl phosphite or appropriate substituted phosphinite.The compounds are useful as stabilizers of organic materials subject to oxidative, thermal and UV light deterioration.