Organic material is stabilized against oxidative degradation by the addition of a small amount of an antioxidant compound or mixture of compounds containing a central segment of one to about ten divalent o-hydrocarbyl phenol groups (e.g. o-tert-butylphenol) bonded to each other through a methylene group and having terminal 3,5-dihydrocarbyl-4-hydroxybenzyl groups at each end. They are made by first condensing o-hydrocarbyl phenol with formaldehyde and then reacting the intermediate with 2,6-dihydrocarbyl phenol and formaldehyde.