While the peppers are grilling, toss the halloumi with 2 tablespoons olive oil. Heat a nonstick frying pan on a hot part of the grill or over a high flame on the stovetop. Place the halloumi cubes in the frying pan and sear, shaking or flipping quickly and gently, until browned on all sides. Remove. Next, place the peach slices on the grill and turn quickly and gently, to brown slightly on all sides.