In a large 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 corn, grill or sauté it until slightly charred. If using frozen corn, cook according to package instructions. Set aside.
In a small bowl, mix together the mayonnaise, sour cream, lime juice, and a pinch of salt. This will be your creamy sauce.
Heat a grill pan or skillet over medium-high heat. Cook the marinated chicken for about 6-7 minutes per side, or until fully cooked and internal temperature reaches 165°F. Remove from heat and let rest for a few minutes before slicing.
To assemble the bowls, start with a base of cooked rice. Top with sliced chicken, corn, a drizzle of the creamy sauce, crumbled cotija cheese, fresh cilantro, and avocado slices.
Serve with lime wedges on the side for an extra burst of flavor.