Wash and dry peppers; place in large bowl. Drizzle with 1 Tbsp olive oil and rub or. brush until well coated. Place peppers on hot grill until blistered, or on a tray in 400 F oven for 25 to 30 minutes, until blackened, turning to cook on all sides, every 10 minutes. Remove peppers to bowl and cover for 10 minutes. Remove lid and allow to cool fully. Once fully cooled, reserve any liquid that accumulated, remove skins and seeds and discard, and slice peppers into ribbons.