1. Defrost the spinach in the microwave or on the stovetop. Spray a 9 X 13-inch glass or ceramic baking dish with nonstick cooking spray. In a large bowl, whisk together the eggs and the milk. Whisk in the cheeses, herbs, garlic powder, and salt. Stir in the spinach, bacon (optional), and bread cubes until the bread is completely moistened. Pour the egg mixture into the baking dish, smoothing it with the back of a spoon, if necessary. Refrigerate it, covered, for at least 4 hours and up to 24 hours.
2. When you are ready to bake it, remove the strata from the refrigerator and preheat the oven to 350ºF. Bake it in the center of the oven, uncovered, for 45–50 minutes until it is browned on the edges and cooked through in the center. Cut it into squares to serve it.

Slow Cooker Directions: In the slow cooker, whisk together the eggs and the milk, then whisk in the cheeses, herbs, garlic powder, and salt. Stir in the spinach and bread cubes until the bread is completely moistened. Cook on low for 4–5 hours or on high for 2–3 hours. (Slow cooker cooking times may vary: Get to know your slow cooker and, if necessary, adjust cooking times accordingly.)

Do Ahead or Delegate: Defrost the spinach, combine and refrigerate the eggs and the milk, shred the cheese, if necessary and refrigerate, combine the dry seasonings, cube the bread, or fully assemble and refrigerate the strata.

Flavor Booster: Double the salt and add 1/8 teaspoon black pepper.