1. Add steak to a large resealable plastic bag, toss in balsamic vinegar, garlic, and brown sugar. Let marinate for 20 minutes at room temperature.
  2. Heat grill to high. Rub steak with vegetable oil, and season generously with salt and pepper.
  3. Grill until desired tenderness, 3 minutes per side for medium-rare. Let rest 5 to 10 minutes, then slice against the grain.
  4. Dressing- In a small bowl whisk together olive oil, and lemon juice, and season with salt and pepper.
  5. Arrange salad: In a large serving bowl, add arugula, peaches, blue cheese or deta, and steak. Drizzle with dressing and gently toss.
  6. Enjoy!