Preheat the grill or grill pan over medium-high heat.
In a mixing bowl, combine the olive oil, chili powder, cumin, salt, and pepper. Add the chicken breasts and coat them evenly with the marinade. Let them marinate for about 10 minutes.
While the chicken is marinating, rinse the rice under cold water. In a pot, add the rice and chicken broth. Bring to a boil, then reduce the heat to low, cover, and cook for about 15-20 minutes, until rice is tender and liquid is absorbed. Fluff with a fork after cooking.
Grill the marinated chicken for 6-7 minutes on each side or until fully cooked (internal temperature should reach 165°F or 75°C). In the last few minutes, add the corn to the grill, turning occasionally until all sides are charred.
Once cooked, let the chicken rest for a few minutes before slicing it into strips.
Remove the corn from the grill and slice the kernels off the cob into a bowl.
In a serving bowl, start with a base of rice, then add sliced chicken, grilled corn, diced red onion, red bell pepper, and avocado. Drizzle with sour cream and lime juice. Sprinkle cotija cheese on top.
Garnish with fresh cilantro before serving.