Place a double layered piece of heavy-duty foil on a tray or cutting board; fold and gather edge to form a rim. Toss the green beans and tomatoes on foil with 1 tablespoon olive oil; season with salt and pepper.
Preheat a grill to medium. Lightly oil the grill grates and season the steak with salt and pepper. Slide the foil tray onto the grill; cook, tossing occasionally, until the beans char slightly and cook through, about 15 minutes.
Meanwhile, add the steaks to the grill; cook until desired doneness, about 5 minutes per side for medium-rare. Remove steaks to cutting board to rest 5 minutes. Slice, and serve steak and the vegetables with the chimichurri sauce.
For the chimichurri sauce: combine the garlic, vinegar, herbs, olive oil and water in small food processor; pulse until herbs are coarsely chopped. Season with salt and pepper.