In a large ziplock bag, combine olive oil, balsamic vinegar, Dijon mustard, minced garlic, and kosher salt and pepper. Add steak and marinate for at least 1 hour.

Preheat grill to high heat (450°F). Grill steak for 4-5 minutes per side until medium doneness (internal temp 140°F). Let it rest for 5-10 minutes before slicing.

Boil water in a large pot. Add corn and boil for 5-7 minutes, then grill for an additional 5-6 minutes until charred. Let cool and slice off kernels.

Heat olive oil in a grilling pan. Grill zucchini for about 2 minutes on each side until tender. Let cool slightly.

In a large mixing bowl, combine spring mix, arugula, chopped endive, halved tomatoes, grilled corn kernels, grilled zucchini, green onions, and herbs. Toss to mix.

Whisk together balsamic vinegar, olive oil, Dijon mustard, and season with salt and pepper. Drizzle over salad and toss gently to coat.

Serve salad arranged on a platter with sliced steak on top, sprinkled with crumbled gorgonzola.