Preheat barbecue plate on high and barbecue grill on medium. Combine the butter, garlic and three-quarters of the parsley in a bowl. Season with salt and pepper and beat until well combined.
Lightly spray both sides of bread and mushrooms with oil. Barbecue the bread on the grill for 2-3 minutes each side until toasted. Barbecue the mushrooms on flat plate, stem side down first, for 3-4 minutes each side until tender. Add the bacon to the hot plate and cook, tossing for 1 minute until golden.
Drain the mushrooms on paper towel. Spread a little garlic butter over each piece of toasted bread. Top each with a mushroom, then sprinkle with bacon and remaining parsley. Drizzle with Worcestershire sauce, season with salt and pepper and serve with lemon wedges.