- Spray 2-quart square or rectangular baking dish with nonstick cooking spray.
- Place 4 slices bread in one layer in prepared dish. Spread roast beef spread evenly over bread slices. Sprinkle 1 1/2 cups cheese and onions over bread. Top with remaining 4 slices bread.
- In large bowl, beat milk, eggs, mustard and cayenne pepper sauce with wire whisk until blended. Pour milk mixture over bread; sprinkle with remaining 1/2 cup cheese. Let casserole stand 30 minutes at room temperature.*
- Meanwhile, preheat oven to 350 degrees. Bake strata 45 minutes until well-puffed and golden brown.
Remove cover and bake as directed.
In very warm climates, cover and refrigerate 1 hour.