Combine first 11 ingredients in a large bowl. Crumble turkey over oats mixture, mixing with hands just until blended. Pack turkey mixture into an 8 x 4-inch loaf pan coated with cooking spray. Combine 1/3 cup ketchup, brown sugar, and 1 teaspoon horseradish in a bowl; stir well. Spread half of ketchup mixture over meat loaf. Bake at 350° for 45 minutes.
Spread remaining ketchup mixture over meat loaf, and bake an additional 10 minutes or until done. Let stand for 10 minutes. Remove meat loaf from pan; cut loaf into 5 slices.