Step 1: Prepare the Marinade

In a large bowl, combine 1/4 cup olive oil, 1/4 cup lime juice, 3 cloves minced garlic, 1 teaspoon ground cumin, 1 teaspoon chili powder, 1 teaspoon smoked paprika, 1/2 teaspoon dried oregano, 1/2 teaspoon ground coriander, 1/2 teaspoon salt, 1/4 teaspoon black pepper, and 1/4 teaspoon cayenne pepper (if using). Mix well to create a smooth marinade.

Step 2: Marinate the Chicken

Add the chicken breasts or thighs to the marinade, ensuring they are well-coated. Cover the bowl and refrigerate for at least 30 minutes, preferably up to 2 hours for maximum flavor.

Step 3: Preheat the Grill

Preheat your grill to medium-high heat (about 375°F to 450°F).

Step 4: Grill the Chicken

Remove the chicken from the marinade and let any excess drip off. Place the chicken on the preheated grill. Grill for about 6-7 minutes on each side, or until the internal temperature reaches 165°F (75°C) and the chicken is cooked through.

Step 5: Serve

Remove the chicken from the grill and let it rest for a few minutes before slicing. Use the grilled chicken for fajitas, serving with warm tortillas, sautéed bell peppers and onions, and your favorite toppings.