In a large pot of boiling salted water, cook green beans until crisp-tender, about 5 minutes. Drain
In same pot, heat 2 teaspoons oil over medium-low. Add garlic; cook until starting to soften, about 2 minutes. Return beans to pot. Add lemon zest and juice, remaining 2 teaspoons oil, and parsley; season with salt and pepper. Toss to coat. Serve immediately.