1. Preheat oven to 350°F; spray a loaf pan with cooking spray.
2. In a large bowl, combine beef, salsa, oatmeal, carrot, tomatoes, and mushrooms. Shape the mixture into a loaf.
3. Place the loaf in the pan. Bake until browned and knife inserted in center comes out clean and hot, about 1 hour and 5 minutes. Let stand about 10 minutes before slicing.