Place croissant pieces in a 9x13 pan. Sprinkle with blueberries.
In a medium bowl, beat cream cheese, sugar, eggs, and vanilla with an electric mixer until well blended. Gradually add milk, beating well after each addition. Pour the mixture evenly over croissant pieces, and let stand 20 minutes.
Bake for 35 to 40 minutes or until set in the center and golden brown. If the tops are browning too quickly, cover with foil for the last 10 minutes of baking.