Preheat oven to 350. Finely chop onion to equal about ½ cup. Combine onion with ground turkey, oats, and Parmesan cheese in a large bowl. Mix well with your hands. In a small bowl, combine eggs, milk, parsley, garlic, red pepper flakes, pepper, and salt, stirring with a whisk. Pour egg mixture over turkey mixture and mix with your hands until combined.

To bake in muffin cups lightly coat each cup of a 12-cup muffin tin with cooking spray. Place an equal amount of turkey mixture into each cup. To bake in a loaf pan, lightly coat a 4 x 8-inch loaf pan with cooking spray. Place turkey mixture in pan and smooth top.

Mix ketchup and barbecue sauce in a small bowl. Spoon evenly over turkey mixture, dividing it equally if using muffin cups. Top with bacon, cutting each strip in half crosswise or layering strips in a lengthwise layer over a large loaf or to distribute equally over muffin cups.

Bake until a meat thermometer inserted into center(s) reaches 165 degrees, about 35 minutes for muffin-sized loaves and 55 minutes for a large loaf. Turn oven to broil. Broil 6 inches from heat for 3-5 minutes or until bacon is crispy and browned. Remove from oven and let sit 10 minutes before serving.