Phenol-containing streams are treated by an oxygen-alkylation process to convert substantially all of the phenol groups to ether groups. The oxygen-alkylation process comprises contacting the phenol-containing stream, preferably a coal liquid, with (a) a basic solution comprising one or more oxides or hydroxides of a metal selected from the group consisting of alkali and alkaline-earth metals; and (b) an alkylating agent represented by the formula RX where R is a C.sub.1 to C.sub.18 alkyl, allyl, cycloalkyl, haloalkyl, benzyl or arylalkyl group provided X is located on the alkyl portion of the compound and X is sulfate or a halide selected from the group consisting of chlorine, bromine and iodine.