This creamy casserole can be made a day ahead, refrigerated, and then baked just before dinner.
Preheat oven to 350 degrees.
Mix the breadcrumbs, 2 tablespoons of the Parmesan cheese, 2 tablespoons melted butter, and 1/2 teaspoon of the Italian seasoning in small bowl and set aside. Cut up any large broccoli or cauliflower florets into bite-sized pieces.
Melt 2 tablespoons butter in large skillet on medium heat. Add the onion and cook about 5 minutes or until tender. Stir in flour, remaining 1 teaspoon Italian seasoning, garlic salt, and pepper. Add the milk and cook until thickened and bubbly. Add cream cheese and remaining 1/4 cup Parmesan cheese and cook, stirring until cream cheese is melted. Add the vegetables and toss gently to coat. Spoon into a 2-quart baking dish. Sprinkle top evenly with crumb mixture.
Bake 40 minutes or until heated through and top is lightly browned.