A savory brunch strata layered with bread, cheese, and vegetables is the ultimate make-ahead family dish. This protein-packed casserole feeds a crowd and can be customized with your favorite fillings.
Preheat oven to 350°F (175°C) and lightly grease a 9x13 inch baking dish with a little olive oil.
Heat 2 tbsp olive oil in a skillet over medium heat; add mushrooms, red bell pepper, and chopped spinach, and sauté for 4-5 minutes until softened. Remove from heat and let cool slightly.
Spread half of the cubed French bread in the prepared baking dish, layer with half the sautéed vegetables and half the shredded cheddar, then repeat to make a second layer.
In a large bowl, whisk together eggs, milk, Dijon mustard, salt, and pepper until thoroughly blended and slightly frothy.
Pour the egg mixture evenly over the bread and vegetable layers, using a spatula to gently press down so all bread is moistened. Let strata sit at room temperature for 20 minutes (or refrigerate overnight for deeper flavor).
Bake uncovered for 45–50 minutes, until the center is just set and the top is golden brown (cover loosely with foil if top browns too quickly).
Let strata rest for 10 minutes before slicing and serving, to help it set and for easier clean slices.