Preheat your oven to 350°F (175°C).

In a large mixing bowl, combine ground beef, Italian-style bread crumbs, chopped onion, eggs, hot wing sauce, milk, Worcestershire sauce, garlic powder, salt, and black pepper. Mix gently until combined, about 1-2 minutes.

Carefully fold in the crumbled blue cheese and shredded mozzarella cheese into the meat mixture.

Transfer the meat mixture onto a greased loaf pan or a baking sheet and shape it into a loaf, about 2-3 inches high.

Place the formed meatloaf into the preheated oven and bake uncovered for 1 hour, until the internal temperature reaches 160°F (71°C).

Remove the meatloaf from the oven and let it rest for 10 minutes before slicing.