Place sausage on a hot grill and cook until done. This may take about 45 minutes.
Heat oil in a saute pan placed on grill. Add red onions, garlic, red bell peppers, and green bell peppers and cook until translucent. Add basil and scallions and cook for a few minutes. Once cooked, cut sausage into 2-inch long pieces, and arrange on serving platter with pepper and onion mixture. Serve with crusty bread or rolls.