Arrange the oysters on a large baking sheet and refrigerate. In a medium skillet, cook the bacon over moderate heat until crisp, about 5 minutes. Drain on paper towels and cut crosswise into 1-inch lengths.
Melt the butter in a saucepan. Add the bell peppers and onion; cook over moderately high heat, stirring often, until softened, 5 minutes. Season with salt and pepper and stir in the parsley. Let cool slightly, spoon over the oysters and top with the bacon.
Light a grill or preheat the oven to 500°. Using tongs, transfer the oysters to the grate and grill over a moderately low fire for 7 to 10 minutes, or until just cooked through. Alternatively, roast the oysters on the baking sheet in the oven. Transfer to a platter and serve at once with lemon wedges.
The recipe can be made through Step 2 and chilled for 5 hours.
The briny oysters and smoky bacon are enhanced by a sparkling wine or crisp, acidic white. From the North Fork, look for Jamesport's nonvintage sparkling wine.