Preheat oven to 375 degrees. Grease a medium baking dish. Cook beef and onion in a large skillet over medium heat until beef is browned and crumbly, about 10 minutes. Drain beef. Sprinkle oregano and garlic salt over the top. Meanwhile, cook pasta according to package directions; drain. Add pasta and spaghetti sauce to skillet and toss. Spoon into prepared baking dish. Sprinkle mozzarella cheese evenly over top of casserole and then sprinkle with Parmesan cheese. Bake until browned, about 30 minutes.
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