Melt margarine/butter in a one quart casserole dish. Add salad dressing, lemon juice, black pepper and garlic powder.
Add shrimp to the casserole dish. Stir gently to cover the shrimp with the mixture. Cover and bake, stirring occasionally for 25 to 30 minutes or until shrimp are pink.
Serve the shrimp hot on a large platter and place the sauce in individual bowls so that you can easily 'dunk' bread in the sauce!
