Preheat oven to 400 degrees.
Spray loaf pan with nonstick spray.
Bring a large skillet sprayed with nonstick spray to medium heat. Cook and stir mushrooms until completely softened, 5 - 7 minutes.
Transfer mushrooms to a large bowl, and pat dry. Add all remaining ingredients except for ketchup. Mix thoroughly.
Transfer mixture to the loaf pan and smooth out the surface.
Evenly spread ketchup over the meatloaf.
Bake until cooked through, about 50 minutes.
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