Cook the macaroni according to the package directions. Drain and set aside.
In a skillet over medium-high heat, brown the ground beef. Remove the beef from the skillet, drain, and set aside.
In the same skillet, cook the bacon. Add the onion. Drain the bacon fat from the pan.
In a large pot, combine the macaroni, beef, bacon, onions, tomato sauce, mushrooms, salt, pepper, garlic salt, and oregano. Simmer for 15 minutes, stirring frequently.
Pour half of the mixture into a large, greased casserole dish and cover with 1/2 cup of each cheese. Then add the remaining macaroni mixture and top with the rest of the cheese.