Preheat the oven to 350F. Cut the hamburgers into quarters. Cut a thin slice from the stem end of each bell pepper, removing seeds.
Cook the onion in oil in a large skillet over medium high heat until tender. Add the rice, garlic powder, and chopped hamburgers with buns (no pickle). Mix 1 ½ can tomato sauce over peppers.
Cover with foil and bake for 20 minutes. Pull from the oven, uncover, and top peppers with cheese. Bake uncovered 20-30 minutes. Garnish with parsley.