1. Preheat a grill: If using a charcoal grill, make a fire in your grill with the coals placed off to one side. When the coals are completely covered in gray ash, hold your hand about 5 inches above the grill grid; count how many seconds you can comfortably leave it there. When you can hold it there for 2 to 3 seconds, you have medium-high heat and are ready to grill. If you are using a gas grill, heat the grill for 15 minutes with the lid closed. Before beginning to cook, reduce the temperature by turning the knobs to medium-high.

2. Place a large heatproof pan on grill near, but not over, the hottest side of the grill. Add butter and garlic and cook until butter is melted, about 3 minutes. Add tomatoes and white wine.

3. Place clams directly over fire on grill and cook until opened, transferring clams to pan as they open. Season clams with salt and pepper; sprinkle with parsley. Serve immediately with grilled bread.