Place beans in a large saucepan and cover with water. Bring to a boil. Cook, uncovered, for 8-10 minutes or until crisp-tender.
Meanwhile, in a small skillet, saute the red pepper, onion and garlic in butter until tender. Remove from the heat; sprinkle with salt and pepper. Drain beans and transfer to a serving dish. Add red pepper mixture and stir gently to coat.