Preheat oven to 375 degrees. Spray 9x13 baking dish with Pam. Add 1/2 cup sour cream to beef and stir to combine, set aside. Combine 1/2 cup sour cream, onion, chilies, and 3/4 cup cheese. Separate 4 biscuits into 8 halves, arrange biscuits on bottom of dish. Spread BBQ mix over biscuits, spread green-chile-cheese mix over beef. Separate remaining biscuits and arrange on top. Bake 20 mins. until biscuits are light brown. Remove from oven and and remaining cheese. Return to oven for 2 mins. to melt cheese. Remove from oven and cut into squares.