1. Preheat broiler to high.
2. To prepare meat loaf, cut bell peppers in half lengthwise; discard seeds and membranes. Place pepper halves, skin sides up, on a foil-lined baking sheet; flatten with hand. Broil 12 minutes or until blackened. Place in a paper bag; fold to close tightly. Let stand for 10 minutes. Peel and finely chop. Place bell peppers in a large bowl.
3. Reduce oven temperature to 350°.
4. Place about one-fourth of mushrooms in a food processor; pulse 10 times or until finely chopped. Transfer chopped mushrooms to a bowl. Repeat procedure 3 times with remaining mushrooms.
5. Heat a large nonstick skillet over medium-high heat. Add oil to pan; swirl to coat. Add mushrooms to pan; sauté 15 minutes or until liquid evaporates, stirring occasionally. Add mushrooms to bell peppers. Wipe pan with paper towels. Add asparagus and onion to pan; sauté 6 minutes or until just tender, stirring occasionally. Add onion mixture to mushroom mixture.
6. Arrange breadcrumbs in an even layer on a baking sheet; bake at 350° for 10 minutes or until golden. Add breadcrumbs and the next 8 ingredients (through eggs) to mushroom mixture, stirring well. Spoon mixture into a 9 x 5-inch loaf pan coated with cooking spray; press gently to pack. Bake at 350° for 45 minutes or until a thermometer registers 155°.
7. To prepare topping, combine 2 tablespoons ketchup and remaining ingredients in a small bowl; brush ketchup mixture over meat loaf. Bake an additional 10 minutes. Let stand 10 minutes; cut into 6 slices.