Preheat the oven to 375°F. In a large bowl, combine the ground beef, diced bacon, ½ cup barbecue sauce, chopped onion, breadcrumbs, egg, salt, and black pepper. Mix until just blended.
Divide the mixture into four equal portions and shape each into a mini loaf. Place the loaves on a baking sheet and brush the tops with the remaining ¼ cup barbecue sauce.
Bake the meatloaves for 25 to 30 minutes until they reach an internal temperature of 160°F.
While the meatloaves bake, heat a 10-inch oven-safe skillet over medium heat with a light coating of butter. In a separate bowl, stir together the cornmeal, flour, baking powder, and salt. Add the milk and melted butter, then mix in the egg until smooth.
Pour the cornbread batter into the hot skillet. Transfer the skillet to the oven and bake for 18 to 20 minutes until the top is golden and a toothpick comes out clean.
Let both the meatloaves and cornbread rest for 5 minutes before serving.