In a large bowl, combine the ground chicken, minced garlic, grated onion, chopped parsley, mint, dried oregano, crumbled feta, breadcrumbs, salt, and black pepper. Mix until evenly distributed.

Divide the mixture into four portions, moisten hands with olive oil, and shape each portion into a patty about ¾ inch thick.

Heat a skillet over medium heat, add olive oil, and cook the patties for about 5-6 minutes per side until golden brown and internal temperature reaches 165°F.

Prepare tzatziki sauce by mixing Greek yogurt, grated cucumber, minced garlic, lemon juice, chopped dill, salt, and pepper until smooth.

Toast burger buns cut side down in the skillet for 1-2 minutes until golden and crispy.

Assemble the burgers by spreading tzatziki on the bottom half of each bun, adding lettuce, a patty, and a slice of tomato, then topping with the other half of the bun.