1. Heat oven to 400ºF. Grease bottom and side of glass pie plate, 9x1 1/4 inches. Mix chicken, onion and seasoning mix. Sprinkle in pie plate.
2. Stir together Bisquick, milk and eggs with fork until blended. Pour into pie plate.
3. Bake 30 to 35 minutes or until knife inserted in center comes out clean. Sprinkle with cheese. Bake 1 to 2 minutes longer or until cheese is melted. Garnish with lettuce, tomatoes and sour cream if desired.
High Altitude (3500-6500 ft) Bake 35 to 40 minutes.
Don't forget to top it off. Serve slices of this savory pie with salsa, sour cream and chopped tomato, or go all out with guacamole and red pepper sauce.