In a large bowl, combine the vegetables, chicken, soup, milk, 1 cup cheese and bacon, if desired. Pour into an ungreased 13 inch x 9 inch x 2 inch baking dish. Cover and bake at 400 for 15 minutes.

Meanwhile, in another bowl, combine biscuit mix and milk. Drop batter by the table spoon fulls on to chicken mixture. Bake uncovered for 20 to 22 minutes or until biscuits are golden brown. Top with onions and remaining cheese. Bake 3 to 4 minutes longer or until the cheese is melted.