1Heat oven to 425°F. In ungreased 2-quart casserole, mix tuna, soup, vegetables and 2/3 cup milk. Bake uncovered 20 minutes.
2In medium bowl, stir Bisquick mix, cheese and 1/2 cup milk until soft dough forms. Drop dough by 6 spoonfuls onto hot tuna mixture.
3Bake uncovered 10 to 12 minutes or until biscuits are golden brown. Mix butter and garlic powder; brush over warm biscuits.