An edible, hardenable coating composition is disclosed containing microcrystalline cellulose, a film forming amount of propylene glycol alginate, and a strengthening polymer, optionally in combination with at least one of a plasticizer, a surfactant, or a filler. The coating composition of the present invention may be applied to pharmaceutical and veterinary solid dosage forms, confectionery, seeds, animal feed, fertilizers, pesticide tablets, and foods and provides an elegant prompt release coating which does not retard the release of active ingredients from the coated substrate.