Cut bread slices into 3/4-inch squares. Place in a single layer on a baking sheet.
Bake at 350° for 10 minutes or until lightly toasted. Set aside.
Drain crabmeat, removing any bits of shell; set aside.
Bring whipping cream and sherry to a boil; boil 5 minutes. Stir in Old Bay seasoning and next 5 ingredients. Gradually add cheese, stirring until blended. Set aside.
Saute celery, green pepper, and green onions in hot oil in a large skillet over medium-high heat 5 minutes or until crisp-tender.
Combine bread cubes, crabmeat, cheese mixture, vegetables, and mayonnaise, tossing gently.
Spoon into a 13-x 9-inch baking dish coated with cooking spray. Bake at 350° for 40 minutes or until bubbly.