Preheat oven to 375°.
Heat a large nonstick skillet coated with cooking spray over medium-high heat; add onion, mushrooms, and carrot. Cook, stirring occasionally, 6 to 8 minutes or until vegetables are tender and all liquid is evaporated. Add garlic; cook 1 minute. Remove from heat; cool slightly.
Combine onion mixture, ground turkey, oats, 1/4 cup ketchup, and next 5 ingredients in a large bowl, mixing well. Press turkey mixture into an 8 x 4-inch loaf pan coated with cooking spray. Brush 2 tablespoons ketchup over top.
Bake at 375° for 55 minutes to 1 hour or until a thermometer registers 170°. Let stand 10 minutes. Remove from pan and slice. Serve with Roasted Red Bell Pepper Sauce.