In a large skillet, cook beef over medium heat until no longer pink; drain. Stir in the tomato sauce, water and pepper. Bring to a boil. Reduce heat; cover and simmer for 15 minutes. Remove from the heat. Stir in vegetables and 1-1/2 cups cheese. Transfer to a greased 13x9-in. baking dish.
Split each biscuit in half. Arrange biscuits around edge of dish, overlapping slightly; brush with butter and sprinkle with oregano. Sprinkle remaining cheese over the meat mixture. Bake, uncovered, at 375° for 25-30 minutes or until the biscuits are golden brown.