Chop cucumbers, onion, grape tomatoes, feta cheese, and olives and place in a medium bowl.
Whisk together oil, vinegar, garlic, oregano, salt, and pepper, to taste.
Pour dressing over chopped Greek salad ingredients and toss until fully coated.
Season beef with salt and pepper, then form into 4 slider-sized patties (3-4 oz. each).
Grill burger patties to desired level (e.g. medium, medium-well, etc.); let rest for 1-2 minutes.
To assemble each burger, place burger patty on bottom bun, then top with greek salad mixture. Add top bun and enjoy!
Greek salad topping adapted from: www.ohsweetbasil.com