Brown the turkey sausage in a large skillet, breaking it into crumbles. Add the peppers and onion and cook for 6 minutes until tender and the skillet is dry. Cool completely.
Butter a 9-by-13-inch dish and layer the bread, sausage mixture and provolone.
Whisk the eggs, milk, salt, pepper and oregano and pour evenly over the layers. Press the bread down once.
Cover and refrigerate for 8 to 16 hours. Let the dish stand out for 30 minutes while the oven heats to 350°F.
Bake uncovered for 50 to 55 minutes, until the center reaches 160°F. Rest for 10 minutes before cutting.