This is an ideal breakfast or brunch to assemble up to a day ahead and bake off in the morning. Healthy cooking doesn't always mean using low-fat products. The full-fat Cheddar and Parmesan together are so satisfying in this easy casserole that a little goes a long way, and they're a terrific complement to lean turkey sausage and spinach.
Total:7 hr(includes refrigerating time)
Heat a large nonstick skillet over medium heat. Add the turkey and scallions and cook, stirring to break up any large chunks, until browned and cooked through, about 10 minutes. Remove from heat and let cool slightly.
Whisk the eggs, egg whites, milk and 1/2 teaspoon each salt and pepper in a large bowl until combined. Add the cooked sausage, spinach, cheeses and bread and toss to distribute the ingredients evenly.
Spray a 3-quart casserole dish with cooking spray. Spread the egg mixture evenly in the dish. Cover and refrigerate for at least 6 hours or preferably overnight.
Preheat the oven to 350 degrees F. Bake the casserole, uncovered, until set and lightly browned on top, about 30 minutes.
Make-Ahead Tip: You can freeze the baked casserole for up to 2 weeks. Cover with foil and reheat at 350 degrees F until hot, 35 to 45 minutes.