Using a food processor or blender, pulse white bread to create rough breadcrumbs measuring 3/4 cup.
Heat a medium, cooking spray coated skillet over medium heat. Combine in skillet, onions, parsley, and garlic. Stir continually and cook for about 5 minutes. Take away from heat and mix in fresh breadcrumbs, Italian breadcrumbs, cheese, lemon juice, and cayenne and black pepper. Align oysters on a baking sheet and spoon mixture equally onto each oyster.
Move oysters to oven and bake for 7 minutes, the edges of the oysters should curl. Garnish with lemon wedges.