Heat oven to 350°F. Spray 8-inch square (2-quart) glass baking dish with nonstick cooking spray.
Heat oil in large skillet over medium heat until hot. Add onions; cook 4 to 5 minutes or until tender, stirring frequently. Add garlic; cook and stir 30 to 60 seconds or until softened. Stir in beans, corn and chicken. Remove from heat.
Cut stack of tortillas in half; cut each half into 1/2-inch strips. Place 1/3 of tortilla strips evenly in bottom of sprayed baking dish. Top with 1/3 of enchilada sauce. Layer with half of bean mixture and half of cheese. Cover with second 1/3 of tortilla strips and second 1/3 of enchilada sauce. Layer with last half of bean mixture and remaining 1/3 of tortilla strips.
Top with remaining enchilada sauce. Sprinkle with remaining half of cheese. Spray sheet of foil with cooking spray. Cover baking dish with foil, sprayed side down.
Bake at 350°F. for 30 minutes. Uncover; bake an additional 8 to 10 minutes or until bubbly.