Preheat oven to 350 degrees.
Heat olive oil over medium-high heat in a large, oven-proof skillet. Add onion and garlic. Soften, stirring occasionally.
Add chicken, corn, tomatoes, cream cheese, sour cream, salt, and pepper. Stir together and bring to a boil. Remove from heat.
Cut tortillas into strips and place over the chicken mixture in the pattern you prefer. Top with cheese and place in oven for about 30 minute or until the casserole is heated through and the cheese is melted.