Boil pierogi according to package directions; drain. Meanwhile, in a large skillet, heat 1 tablespoon oil over medium heat. Add kielbasa, pepper and onion; cook and stir 10-12 minutes or until sausage is browned and onion is tender. Remove from pan., In same skillet, heat remaining oil over medium heat. Add pierogi; cook and stir 1-2 minutes or until lightly browned. Return kielbasa mixture to pan; heat through.