Use a sharp knife to cut the tops and tails off the green beans. Discard the tops and tails.
In a large mixing bowl, add the green beans. Drizzle with olive oil, then sprinkle with salt and pepper to taste.
Toss gently to evenly coat the beans.
Preheat the grill to medium-high (375°F to 450°F).
Arrange the green beans in a single layer in a grill basket. Place onto the hot grill. Cook for 4–6 minutes per side, tossing or shaking the basket halfway through, until the beans are tender-crisp and charred in spots.
Transfer the grilled beans to your serving dish and top with butter if desired. Serve immediately.