Preheat oven to 400℉.
In a greased pie plate, add 2 cups cut up chicken, 1½ cups drained thawed peas, 1½ cups drained thawed carrots, ¼ cup chopped mushrooms, and ¼ cup chopped onions. Combine well and set aside.
In a separate bowl, add 1⅓ cups milk, 4 eggs, ¾ cup baking mix, ½ teaspoon salt, and ¼ teaspoon pepper. Beat 15 seconds in a blender or 1 minute using a hand beater and pour into pie plate.
Bake approximately 30 to 35 minutes or until a knife inserted comes out clean. Cool for 5 minutes.