In a large bowl, whisk garlic, lime juice, cumin, chili powder, and 1 tablespoon vegetable oil until smooth. Season with salt and pepper to taste.
Arrange chicken in marinade until evenly coated. Cover bowl, transfer to refrigerator, and allow chicken to marinate at least 2 hours or up to 12.
Preheat oven to 400F and lightly grease a large sheet pan. Arrange peppers and onion on pan and toss with remaining 1 tablespoon vegetable oil and salt and pepper to taste. Remove chicken from marinade and arrange on sheet pan with sliced peppers and onion.
Bake chicken at 400F 20-25 minutes until chicken registers 165F and peppers/onions are tender. Allow to cool slightly, then thinly slice chicken into strips and toss back into peppers and onions.
Assemble rice bowls by dividing rice between serving bowls and topping with chicken, peppers, and onions mixture, avocado, and tomatoes. Garnish bowls with tortilla chips, sour cream, cilantro, and squeeze fresh lime wedges over top. Enjoy!