Heat oven to 350 degrees. Coat 13 x 9 x 2-inch baking dish with nonstick spray. Stir cream cheese, scallions, milk and Old Bay seasoning in bowl until smooth. Stir in peppers, reserving 1/2 cup, and broccoli, reserving 1 cup. Add crabmeat, 1 egg, salt and pepper. Whisk remaining egg into alfredo sauce.
Spread 1/3 cup alfredo sauce into baking dish. Top with 3 noodles, one-third of the crab mixture and one-fourth of alfredo sauce. Repeat layering twice. Top with 3 noodles; sprinkle with reserved red peppers and broccoli. Pour on remaining alfredo sauce. Sprinkle with Parmesan.
Bake, covered, at 350 degrees for 30 minutes. Uncover; bake an additional 20 to 25 minutes, until browned and bubbly. Let stand 10 minutes.