In a large skillet over medium high heat, brown ground beef and drain excess fat. Stir in onions and peppers and cook until the vegetables are tender, about 5 minutes.

Stir in chili seasoning mix and diced tomatoes. Bring to boil and reduce heat to low. Simmer uncovered until chili is thickened, about 10 minutes. Season with salt and pepper to taste.

To assemble, split open potatoes with a knife lengthwise. Spoon chili into the center of each potato then top with cheese. If desired, place stuffed potatoes under the broiler or oven until cheese is melted.