Impossible Broccoli Pie
["2 (10 oz. each) pkg. frozen, chopped broccoli", "1 c. (4 oz.) Cheddar cheese, shredded", "1 c. (4 oz.) Mozzarella cheese, shredded", "1 c. (4 oz.) Monterey Jack cheese, shredded", "2/3 c. onion, chopped", "1 1/3 c. milk", "3 eggs", "3/4 c. buttermilk baking mix", "3/4 tsp. salt", "1/4 tsp. pepper"]
["Heat oven to 400\u00b0.", "Grease 10 x 1 1/2-inch pie pan."]
["broccoli", "Cheddar cheese", "Mozzarella cheese", "cheese", "onion", "milk", "eggs", "buttermilk baking mix", "salt", "pepper"]