Cook pasta to desired doneness as directed on package. Drain; return to saucepan.
Meanwhile, heat oven to 350°F. Spray 12x8-inch (2-quart) glass baking dish with nonstick cooking spray. Melt 1/4 cup margarine in medium saucepan over medium-high heat. Add flour; cook and stir until well blended. Gradually add half-and-half, cooking until mixture boils and thickens, stirring constantly. Stir in seasoned salt and pepper.
Add cooked pasta; toss to coat. Spread 1/3 of pasta mixture evenly in sprayed baking dish. Sprinkle with 1 cup of the cheese. Repeat layers.
In small bowl, combine topping ingredients; mix well. Sprinkle over top of casserole.
Bake at 350°F. for 30 to 35 minutes or until casserole is bubbly and topping is golden brown.