In a large bowl, whisk together eggs, 1 1/2 cups milk, 1 tablespoon cinnamon, 3 teaspoons vanilla, and baking powder until smooth.
Add bread cubes and toss until fully coated.
Pour mixture into a greased 9x13-inch baking dish. Cover and refrigerate for at least 4 hours or overnight.
Preheat oven to 350°F (175°C). Remove casserole from refrigerator.
Mix melted butter, brown sugar, and remaining cinnamon. Drizzle over casserole and let sit for 10–15 minutes.
Bake for 20–25 minutes until golden brown. Let rest for 5 minutes.
In a bowl, mix cream cheese, confectioners’ sugar, remaining vanilla, and milk until smooth.
Drizzle glaze over the Cinnamon Roll Casserole before serving.