Bring a large pot of salted water to a boil. Add the beans and cook until crisp-tender, about 4 minutes. Drain well.

Heat the oil in a large skillet. Add the orange and lemon zests and garlic and cook for 1 minute. Add the orange juice and cook until the juice reduces by half and starts to thicken, 3 – 4 minutes. Add the beans and butter and toss well until the beans are heated through and coated. Season with salt and pepper. Serve.