In a skillet, heat olive oil over medium heat. Add diced chicken and season with chili powder, cumin, garlic powder, salt, and black pepper. Cook until the chicken is browned and cooked through, about 7-10 minutes.

While the chicken is cooking, prepare the brown rice according to package instructions.

In a large mixing bowl, combine the cooked rice, black beans, corn, cherry tomatoes, and cooked chicken. Squeeze lime juice over the mixture and toss to combine.

Serve the mixture in bowls and top with shredded lettuce, cheddar cheese, sliced avocado, and chopped cilantro.