Heat oven to 400°F. Spray square pan, 9x9x2 inches, with cooking spray. Cook beef in 10-inch skillet over medium-high heat 5 to 7 minutes, stirring occasionally, until brown; drain. Stir in salsa. Spread beef mixture in pan.
Stir Bisquick mix, milk, onion and cheese in medium bowl until soft dough forms. Drop dough by 12 tablespoonfuls over mixture in pan.
Bake uncovered about 25 minutes or until golden brown and toothpick inserted in biscuits comes out clean.