In a medium bowl, combine the olive oil, chili powder, garlic powder, cumin, salt, and pepper. Add the chicken breasts and coat them evenly with the spice mixture. Let marinate for at least 15 minutes.

While the chicken is marinating, prepare the corn. If using fresh or frozen corn, sauté it in a skillet over medium heat for about 5-7 minutes until heated through and slightly charred. If using canned corn, simply drain and set aside.

In a small bowl, mix together the mayonnaise, lime juice, and half of the chopped cilantro. Set aside.

Heat a grill or grill pan over medium-high heat. Cook the marinated chicken for about 6-7 minutes on each side or until fully cooked and the internal temperature reaches 165°F. Remove from heat and let rest for a few minutes before slicing.

To assemble the bowls, divide the cooked rice among four bowls. Top each with sliced chicken, sautéed corn, crumbled feta, and a drizzle of the lime mayo.

Garnish with avocado slices, the remaining cilantro, and serve with lime wedges on the side.