Preheat the oven to 400 degrees F.
Combine the sweet potatoes, butter, vegetable oil, peppers, onion, chili powder and granulated garlic in a large mixing bowl. Season with some salt and pepper and toss, making sure everything is coated evenly. Spread the mixture out onto a baking tray and place in the oven. Bake until the potatoes are knife tender with a crispy exterior, about 20 minutes, stirring twice during the cooking process.
Remove the hash from the oven, increase the oven temperature to broil and broil for 5 minutes to brown. To finish, toss the potatoes with the chopped parsley and season with salt and pepper.