Chicken and Stuffing Casserole

1 1/2 c. cooked chicken 1 can cream of chicken soup
1/2 can evaporated milk 1 small pkg frozen peas
1 pkg. prepared dressing 3/4 c. margarine
1 chopped onion 2 stalks celery

Saute celery and onions in margarine ( I used celery salt and onion powder). Pour over dressing and moisten with chicken brother. Place 1/2 the dressing in bottom of 9 x 13 pan. Mix peas, soup, milk and chicken. Spoon over dressing. Cover with remaining dressing. Bake at 300 degrees for 30 mins.