• Add steak to a large Ziploc bag or baking dish and toss in balsamic vinegar, garlic and brown sugar.
• Let marinate 20 at room temperature.
• Heat a grill or grill pan to high.
• Rub steak with vegetable oil and season generously with salt and pepper.
• Grill until desired doneness, 3 per side for medium rare.
• Let rest 5, then slice.
• Meanwhile, make dressing: In a small bowl whisk together olive oil and lemon juice and season with salt and pepper.

Arrange salad:

• In a large serving bowl, add arugula, peaches, blue cheese or feta, and steak.
• Drizzle with dressing and gently toss.
• Serve immediately.