A composite shingle having unitary construction is presented that includes a body shell, a plurality of longitudinal ribs, and a plurality of rib stiffeners. The present composite shingle may also include transverse ribs, a depressed nailing zone, nailing zone ribs, and / or at least one alignment aid. The plurality of rib stiffeners may include a material saving profile. Further, the dimensions of the composite shingle more closely resemble true slate and shake shingles and at least a portion of the outside face of composite shingle may be textured to resemble slate or wood shake shingles.A plurality of assembled composite shingles of the present invention is also claimed as part of this invention. Finally, a method of applying multiple courses of shingles on a roof including the composite shingle of the present invention is presented.