Step 1

Combine 1/4 cup olive oil, lemon juice, 2 cloves minced garlic, oregano, and 1/2 teaspoon salt in a large resealable bag. Add chicken, coat with the marinade, squeeze out excess air, and seal the bag. Marinate in the refrigerator for 2 hours.

Step 2

Mix yogurt, cucumber, 1 tablespoon olive oil, vinegar, 1 clove minced garlic, and 1 pinch salt together in a bowl. Refrigerate tzatziki sauce for flavors to blend, 1 to 2 hours.

Step 3

Preheat an outdoor grill for medium-high heat and lightly oil the grate. Soak wooden skewers in a bowl of water for about 15 minutes.

Step 4

Remove chicken from marinade and thread onto the soaked skewers. Discard unused marinade.

Step 5

Cook the skewers on the preheated grill, turning frequently until nicely browned on all sides and chicken is no longer pink in the center, about 8 minutes per side. Serve with tzatziki sauce.