Heat oven to 350°F. Spray 11x7- or 12x8-inch (2-quart) glass baking dish with cooking spray. In large bowl, beat egg and milk with wire whisk until smooth.
Separate dough into 8 biscuits; cut each into quarters. Gently stir biscuit pieces into egg mixture to coat evenly. Fold in bacon, cheese and onions. Spoon mixture into sprayed dish; arrange biscuit pieces in single layer.
Bake at 350°F. for 23 to 28 minutes or until golden brown. Cut into squares.