A method of forming a composite closure, comprising the steps of: providing an outer closure cap including a top wall portion, and an annular skirt portion depending from said top wall portion, said skirt portion including an inwardly extending, annular seal lip positioned in closely spaced relationship to said top wall portion to define an annular recess; providing a quantity of molten, liner-forming plastic material in the form of a pellet, and positioning said pellet within said outer closure cap adjacent the top wall portion thereof; and advancing a liner-forming tooling assembly into said closure cap to compression mold said quantity of molten plastic material to form a sealing liner adjacent said top wall portion of said closure cap, said sealing liner including a central portion, and an annular sealing bead portion at least partially positioned within said annular recess, said advancing step including advancing an outer sleeve of said tooling assembly into said closure cap to engage said annular seal lip, and thereafter advancing an inner plunger of said tooling assembly relative to said outer sleeve to compression mold said quantity of plastic material, including controlling the flow of the molten plastic material circumferentially of said annular recess, as the molten plastic material is compression molded, by providing said outer closure cap with a plurality of radially-oriented gussets circumferentially spaced about and positioned within said annular recess, characterized in that each of said gussets extends vertically from said annular seal lip to said top wall portion, and each having an inner edge positioned in substantial alignment with an inside diameter of said annular seal lip, thereby defining a plurality of compartments in said annular recess between adjacent ones of said gussets, which during liner formation facilitate venting of air from within said annular recess) to the vent provided in the tooling assembly. providing an outer closure cap including a top wall portion, and an annular skirt portion depending from said top wall portion, said skirt portion including an inwardly extending, annular seal lip positioned in closely spaced relationship to said top wall portion to define an annular recess; providing a quantity of molten, liner-forming plastic material in the form of a pellet, and positioning said pellet within said outer closure cap adjacent the top wall portion thereof; and advancing a liner-forming tooling assembly into said closure cap to compression mold said quantity of molten plastic material to form a sealing liner adjacent said top wall portion of said closure cap, said sealing liner including a central portion, and an annular sealing bead portion at least partially positioned within said annular recess, said advancing step including advancing an outer sleeve of said tooling assembly into said closure cap to engage said annular seal lip, and thereafter advancing an inner plunger of said tooling assembly relative to said outer sleeve to compression mold said quantity of plastic material, including controlling the flow of the molten plastic material circumferentially of said annular recess, as the molten plastic material is compression molded, by providing said outer closure cap with a plurality of radially-oriented gussets circumferentially spaced about and positioned within said annular recess, characterized in that each of said gussets extends vertically from said annular seal lip to said top wall portion, and each having an inner edge positioned in substantial alignment with an inside diameter of said annular seal lip, thereby defining a plurality of compartments in said annular recess between adjacent ones of said gussets, which during liner formation facilitate venting of air from within said annular recess) to the vent provided in the tooling assembly.