1. Combine turkey, garlic powder, celery salt, and pepper; mix well, and shape into 12 thin patties.
2. Combine green pepper, green onions, and mushrooms; spoon 2 rounded tablespoons of vegetable mixture on top of half the patties.
3. Top each with half of a cheddar cheese slice and a remaining turkey patty, sealing edges.
4. Wrap bacon around each patty and secure with toothpick.
5. Place patties on greased broiler rack; bake at 350 for 20 minutes or until done.
6. Place under broiler for an additional 2 minutes or until bacon is browned.