Set out a large 9 x 13 inch baking dish. Zest the lemons, then cut and juice them.
Add the Greek yogurt, olive oil, lemon juice, lemon zest, oregano, garlic, paprika, crushed red pepper flakes, 1 tablespoon salt, and 1 teaspoon black pepper to the dish. Mix well.
Add the chicken pieces and turn to coat thoroughly in the marinade.
Cover and refrigerate for at least 4 hours, or up to 24 hours.
To grill: Preheat grill to medium heat (350-400°F). Cook chicken for 5-6 minutes per side until fully cooked.
To bake: Preheat oven to 400°F. Place chicken on a parchment-lined baking sheet in a single layer and bake for 15-20 minutes.
Garnish with parsley before serving.
Notes
Marinating overnight yields deeper flavor and more tender chicken.
Chicken breasts may cook faster than thighs; adjust time accordingly.
Use fresh lemon juice for best flavor.
Serve with rice, salad, or flatbread for a complete meal.
Leftovers can be stored in the refrigerator for up to 3 days.