Heat oven to 425°. Mix mayonnaise and 2 tablespoons baking mix in medium bowl until well blended. Stir in turkey, cheese, celery, bell pepper and onions; set aside.
Stir remaining ingredients just until soft dough forms. Place on surface sprinkled with baking mix; roll in baking mix to coat. Knead 10 times. Divide dough into 24 pieces; shape into balls. Place close together (stack balls if needed) around edge of ungreased 2-quart casserole.
Spoon turkey mixture into mound in center of biscuits. Bake uncovered 20 to 22 minutes or until biscuits are golden brown and turkey mixture is hot.