Heat your oven to 350°F and grab a 9x13 baking dish. Coat it lightly with the olive oil, making sure to get the corners and sides. This prevents sticking and helps everything brown evenly. Toss the bread cubes into the dish first, spreading them out in a single layer.

Layer your shredded chicken and diced turkey over the bread, then scatter the carrots, red bell peppers, and spinach across the top. Sprinkle the mozzarella cheese evenly over everything—don't skip this step because it gets all melty and golden. The mixture should look pretty packed at this point, which is exactly what you want.

In a separate bowl, whisk together the 3 eggs, whole milk, butter, dried thyme, salt, and black pepper until you don't see any streaks of egg white. Pour this mixture slowly over all the layers, letting it seep down through the bread and veggies. Pro tip: I let mine sit for a minute before pouring so the bread soaks it up better.

Gently stir everything together with a fork, making sure the bread cubes get coated and the ingredients distribute evenly. Don't overmix—you're not making scrambled eggs here, just combining everything gently. The casserole should look slightly wet on top, which means the custard will cook through beautifully.

For the make-ahead magic, cover your Easter brunch casserole recipe with plastic wrap and refrigerate overnight (or up to 12 hours). When you're ready to bake, let it sit on the counter for 15 minutes while the oven preheats to 350°F. This room-temperature start prevents the edges from overcooking before the center sets.

Place the casserole in the preheated oven and bake for 40-45 minutes until the top is golden brown and a knife inserted in the center comes out clean or with just a few wet crumbs. Don't panic if it jiggles slightly in the very center—it'll firm up as it cools. Mine always looks slightly underdone at first, but trust the timing.

Remove from the oven and let it rest for 5 minutes before serving. This resting time is crucial because it lets the egg set completely and makes it way easier to cut into neat squares. The kitchen's gonna smell absolutely incredible at this point.