Spray a 9x13 inch baking dish with nonstick spray. Place the pepperoni bread cubes in the dish. Stir in the peppers and onions and garlic until evenly dispersed. Stir in the chives and about three quarters of the grated cheeses, leaving a bit to sprinkle on top.
In a large bowl, whisk together the milk, mustard, salt, paprika, oregano and pepper together until combined. Pour the egg mixture over top of the mixture. Sprinkle the remaining cheese on top.
Cover the dish and refrigerate it overnight.
The next morning, preheat the oven to 350 degrees F. I like to take the dish out of the fridge about an hour before so it comes to room temperature.
Bake the strata for 50 to 60 minutes, or until a tested inserted in the center comes out clean. Sprinkle with extra parmesan cheese. Serve immediately with your choice of condiments, like hot sauce or extra fresh herbs!