Impossible Taco Pie
["1 lb. ground beef", "1/2 c. chopped onion", "2 envelopes (1 1/4 oz. each) taco seasoning mix, dry", "3/4 c. Bisquick baking mix", "1 1/4 c. milk", "3 eggs", "1 c. shredded Cheddar cheese (4 oz.)", "1/4 head lettuce, shredded", "1 tomato, diced", "1/4 c. sliced ripe olives"]
["Grease pie plate, 10 x 1 1/2-inches, or square baking dish, 8 x 8 x 2-inches.", "Cook and stir ground beef and onion in 10-inch skillet until beef and onion are brown; drain.", "Stir in seasoning mix; spoon into pie plate."]
["ground beef", "onion", "taco", "Bisquick baking mix", "milk", "eggs", "Cheddar cheese", "head lettuce", "tomato", "olives"]