The present invention provides supported peroxides, and a method of forming supported peroxides. Supported peroxides according to the invention are solid particles that include an organic peroxide, a metallic soap, and a polymer. In accordance with the method of the invention, supported peroxides are preferably formed by dispersing a mixture that includes at least one peroxide and at least one C4 to C30 carboxylic acid into an aqueous solution that includes a compound that is capable of reacting with the C4 to C30 carboxylic acid to form a water soluble soap. Dispersing the mixture into the aqueous solution results in the formation of an emulsion. Polymer is then added to the emulsion, and forms a polymer suspension. A polyvalent metal compound that is capable of reacting with the water soluble soap to form a water insoluble metallic soap is then added to the polymer suspension, which converts the water soluble soap into a water insoluble metallic soap that precipitates from the suspension. The organic peroxide and the polymer are entrained within the precipitate.