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

Divide into four portions and shape into patties about ¾ inch thick with an indentation in the center.

Cover patties with plastic wrap and refrigerate for at least 30 minutes.

Heat 2 tablespoons of olive oil in a skillet over medium heat.

Cook patties for 5-6 minutes on each side until golden brown and internal temperature is 165°F (75°C).

In a separate bowl, prepare tzatziki 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.

Assemble burgers with tzatziki sauce, lettuce, patties, and tomato slices.