Chop the onion and green pepper. Drain and rinse the canned beans. Cook macaroni per instructions and drain. In a large skillet heat oil over medium high heat. Add onion, green pepper, garlic, chili powder, salt and cumin; saute for about 4 minutes until vegetables are tender. Stir in the tomatoes (undrained) breaking them with a spoon. Add kidney beans and corn (already thawed); bring to a boil. Reduce heat to simmer and continue cooking for 15 minutes stirring occasionally. Toss in cooked macaroni. Sprinkle with the shredded cheese.