Spray a 10 inch x 14 inch casserole with cooking spray.
Slice croissant in half vertically.
Arrange in bottom of casserole.
Top with berries. Set aside.
In a large bowl, whisk together eggs, milk, cream, butter, sugar, vanilla, and lemon zest.
Ladle over top of berries.
Allow to stand for 30 minutes before baking.
While casserole is standing, heat oven to 350°F.
Bake for 1 hour 40 minutes, covering after 35 minutes.
Let rest for 15-20 minutes before serving.