In a small bowl, whisk together chili powder, cumin, garlic powder, oregano, paprika, salt, cayenne, and pepper.
Rub chicken breasts all over with the spice mixture.
Add 1 Tbsp olive oil to a large skillet over medium heat. Place chicken in skillet and cook for 5-7 minutes on each side until golden and cooked through. Remove to cutting board and once cool enough to touch, dice and put in a medium bowl.
In the same pan you cooked the chicken in (add more olive oil if needed), add onions and bell peppers. Cook for 3 minutes to soften a bit. Add corn and black beans and cook for another minute to heat through. Add mixture to chicken in bowl and toss to combine.
Either clean out the skillet you've been using or heat a griddle to medium heat (I like to use a griddle because I can cook a few quesadillas at a time). Brush one side of each tortilla with olive oil.
Place a tortilla oil-side down in the skillet. Top with some shredded cheese and about ½ cup of the chicken mixture. Sprinkle more cheese on top and top with another tortilla oil-side up.
Cook for 2-3 minutes, until cheese melts and tortilla gets crispy. Use a spatula to flip the quesadilla over and cook for another minute, or until the second side is also crispy. If the tortilla starts curling up, just use a spatula to press it down. Repeat with remaining tortillas, cheese, and chicken mixture.
Place quesadillas on a cutting board and cut each into quarters. Serve with sour cream, salsa, avocado, cilantro, and any other toppings you desire.