Preheat oven to 350°.
Melt margarine in a Dutch oven over medium-high heat. Add 1 1/2 cups onion, bell pepper, celery, and garlic; sauté 5 minutes or until tender. Add bread and next 6 ingredients (bread through oysters); cook 7 minutes or until done, stirring constantly. Remove from heat; stir in green onions and cheese. Spoon into a 13 x 9-inch baking dish coated with cooking spray. Bake at 350° for 30 minutes.
Yum, yum and yum! Been making this for many years and it's always yummy!