Cut the top from the pumpkin and scrape out seeds and fibers. Simmer in salted water (to cover) for 15 to 25 minutes or until tender and hot to touch. Drain. Brown beef and onion in 1 tablespoon oil. Add red pepper, green pepper, and garlic. Cook 1 minute longer. Remove from heat and stir in remaining ingredients. Spoon in remaining ingredients; add into pumpkin. Place on lid. Brush outside of pumpkin with oil and bake at 350 degrees for 1 hour. Let stand 10 minutes. Cut wedge out of the side to serve.