In a large bowl, mix together the bell peppers, tomatoes, half of the garlic, the olive oil, half of the vinegar, the oregano, sugar, salt and pepper. Mix well and spread out in a single layer in a large baking pan.
Roast the vegetables for about 20 minutes. Remove from the oven, turn the vegetables so that they will brown evenly, and return them to the oven. Continue to roast until the peppers are slightly charred at the edges and the tomatoes are soft and tender and have begun to form a sauce, about 10 minutes more.
Remove from the oven and sprinkle with the remaining garlic to taste and the remaining vinegar. Let cool until warm or room temperature. Garnish with the basil just before serving.
Recipe Notes
Adapted from Williams Sonoma (www.williams-sonoma.com)