Preheat the broiler. Cover a heavy baking sheet with foil. Arrange the bell peppers on the baking sheet. Broil
until the skins brown and blister, turning the peppers over occasionally, about 15 minutes. Enclose the peppers in a resealable plastic bag. Set aside until cooled to room temperature, about 20 minutes.
, and cut the peppers into 1/2-inch thick strips. Toss the pepper strips, olives, oil, capers, basil, garlic, salt, and pepper in a medium bowl to combine. Cover and refrigerate up to 2 days.