In a large bowl, whisk together olive oil, lemon zest, lemon juice, chili powder, cumin, garlic powder, salt, and pepper.
Add chicken thighs to the marinade, coat thoroughly, and refrigerate for 30 minutes.
Preheat an outdoor grill or indoor grill pan to medium-high heat (approximately 400°F).
Place chicken on the grill and cook for 6 to 8 minutes per side, or until the internal temperature reaches 165°F.
Transfer chicken to a cutting board and let rest for 5 minutes before slicing into strips.
In a separate bowl, combine the warm cooked rice with cilantro and lime juice.
Divide the rice into four bowls and top with sliced chicken, corn, black beans, avocado, and red onion.