How to Make It
Heat the grill to medium. Season the steak with the pepper and coat with 1 tablespoon of the oil. Grill, turning once, until a thermometer inserted in the center of each piece registers 130°F, 5 to 7 minutes per side for medium-rare. Remove and let rest 5 minutes before slicing against the grain.
Meanwhile, toss together the corn, zucchini, scallions, and 1 tablespoon of the oil. Grill the corn and vegetables, turning occasionally, until charred and tender, 6 to 7 minutes; remove. Cut the kernels from the cobs and cut the vegetables into pieces; toss together.
Pulse the arugula, oregano, and garlic in a food processor until roughly chopped. Add the vinegar, water, salt, and the remaining oil and pulse until smooth. Divide the steak and succotash among 4 plates. Drizzle with the dressing.