01 - Whisk together olive oil, lime juice, garlic, cumin, paprika, chili powder, oregano, salt, and pepper in a medium bowl until fully combined.
02 - Add chicken thighs to the marinade, toss well to coat evenly, and let sit for at least 15 minutes. For deeper flavor, refrigerate up to 2 hours.
03 - Heat a large skillet or grill pan over medium-high heat. Cook chicken thighs for 5–6 minutes per side until cooked through and nicely browned.
04 - Transfer chicken to a cutting board and let rest for 3 minutes. Chop into bite-sized pieces.
05 - Heat corn tortillas in a dry skillet or directly over a gas flame for about 30 seconds per side until soft and pliable.
06 - Fill each tortilla with chopped chicken. Top with diced onion, cilantro, avocado slices, and cotija cheese if desired.
07 - Serve immediately with lime wedges and salsa or hot sauce on the side.