1. Heat oven to 350ï¿½. Coat an 8-inch square baking dish with cooking spray; set aside.
2. Bring a large pot of water to a boil over high heat; add noodles, and cook 7 minutes or until al dente. Drain and set aside.
3. Reduce heat to medium; add margarine, and cook until margarine melts. Add flour, salt, and pepper; cook 1 to 2 minutes until flour begin to brown. Stir in milk, 1/2 cup at a time, whisking well to ensure a smooth sauce. Stir in cheeses; whisk until completely melted. Stir in cooked noodles. Transfer mixture to prepared baking dish.
4. Top noodles with breadcrumbs; bake at 350ï¿½ for 20 minutes or until top begins to brown and cheese is bubbly.
5. While noodles bake, place roasted bell pepper and yogurt in a blender or food processor; process until smooth. Drizzle over squares of baked noodles and serve.