In a medium bowl stir together the chili powder, salt, cumin, onion powder, and, if desired, red pepper. Add the chicken; toss to coat. In a large nonstick skillet heat oil over medium-high heat. Add chicken to skillet. Cook and stir for 2 to 3 minutes or until chicken is no longer pink. Stir in corn; heat through.
Meanwhile, warm the taco shells according to package directions. Fill the taco shells with chicken mixture. Top with lettuce, tomato, and cheese. Makes 2 servings.