Lightly spray a 9-inch square baking dish, or similarly sized baking dish, with nonstick cooking spray. Cut or tear croissants into bite-size pieces and place them in the prepared dish. Evenly distribute the berries over the croissant pieces. (If berry pieces are too large, cut into bite-size pieces.)
In a medium bowl, beat the cream cheese and sugar until smooth and creamy. Add eggs and vanilla, beat until combined. Gradually beat in milk. Pour mixture evenly over the croissant pieces and berries. Let stand for at least 20 minutes, or cover and refrigerate overnight.
Preheat oven to 350°F/175°C. Bake for 30-40 minutes, or until set in the center and golden brown. (Cover with foil for last 10 minutes if the top is getting too browned.)
Serve warm with powdered sugar, ice cream, or whipped cream.