01 - In a medium bowl, whisk together olive oil, lime juice, garlic, cumin, paprika, chili powder, oregano, salt, and pepper until thoroughly combined.
02 - Add chicken thighs to the marinade, toss well to coat completely, and let sit for at least 15 minutes, up to 2 hours for deeper flavor penetration.
03 - Heat a large skillet or grill pan over medium-high heat. Cook chicken thighs for 5 to 6 minutes per side until cooked through and nicely browned.
04 - Transfer chicken to a cutting board, let rest for 3 minutes to retain juices, then chop into bite-sized pieces.
05 - Warm the 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 for added zest.