Preheat oven to 350. Place hamburger in a large bowl and add eggs with 1/2 cup ketchup. Fold gently to assure you will have a tender meatloaf. Add breadcrumbs, oregano, mushrooms and onion after egg and ketchup mixture is finely folded with hamburger.
Take half of the meatloaf mixture and place into a baking dish and add 9 slices of cheese evenly on the first layer. After cheese has been placed, add the second half of the mixture on top of the cheese. Put 3 tablespoons of ketchup on top and criss cross with a fork to spread it evenly over the top layer. Sprinkle salt, pepper and oregano over the top layer with ketchup and bake for 1 hour and 10 minutes.
Take meatloaf out and let rest, then cut serve and enjoy!