Heat oven to 400 degrees. Grease pie plate (10 x 1 1/2). Rinse broccoli under running cold water to thaw; drain thoroughly. Mix broccoli, 2 cups of the cheese and onion in plate. Beat milk, eggs, baking mix, salt and pepper until smooth, 15 seconds in blender on high or 1 minute with hand beater. Pour into plate. Bake until knife inserted in center comes out clean, 25-35 minuets. Top with remaining cheese. Bake just until cheese is melted, 1-2 minutes longer. Cool 5 minutes. Yield 6-8 servings.