Spray 13x9-inch (3-quart) glass baking dish with cooking spray. Melt margarine in 12-inch skillet over medium-high heat. Add leeks and asparagus pieces; cook and stir 5 to 6 minutes or until crisp-tender.
Add potatoes, roasted pepper strips, salt and dill; mix lightly. Spoon evenly into sprayed baking dish.
Beat eggs in medium bowl. Add half-and-half; beat well. Add half of the cheese; mix well. Pour over vegetable mixture in baking dish. Sprinkle with remaining half of cheese. Cover with foil; refrigerate at least 8 hours or overnight.
Heat oven to 350°F. Bake, covered, 45 minutes. Uncover; bake an additional 20 to 25 minutes or until center is set. Let stand 10 minutes. Cut into squares. If desired, garnish with red bell pepper strips.