In a mixing bowl, whisk together fresh lemon juice, minced garlic, dried oregano, and olive oil until well combined. Add the chicken breasts, ensuring they are coated in the marinade. Cover the bowl and refrigerate for at least 30 minutes.

In a separate bowl, combine Greek yogurt with chopped cucumber, fresh dill, and a squeeze of lemon juice. Season with salt and pepper and refrigerate to chill.

Preheat your grill to medium-high heat. Remove the chicken from the marinade and grill for about 6-7 minutes per side until the internal temperature reads 165°F.

Slice the grilled chicken into strips. Warm pita bread, layer with chicken, tzatziki sauce, lettuce, and tomatoes.

Serve immediately for best flavor, optionally with sides like Greek salad or roasted potatoes.