Bring foil up around peppers to enclose. Let stand about 15 minutes or until cool. Loosen edges of the skins with a small sharp knife; gently pull off skins in strips and discard. Place peppers in food processor or blender. Cover; process or blend until smooth.
In large skillet cook onion and garlic in hot olive oil over medium heat 4 minutes or until tender. Stir in pureed peppers, white wine vinegar, sugar, thyme, oregano, 1/2 teaspoon salt, and 1/4 teaspoon black pepper. Bring to boiling. Reduce heat. Simmer, uncovered, 6 minutes or until desired consistency. Makes 2 cups sauce.