Sauté onion and bell pepper in a large skillet coated with cooking spray over medium-high heat 5 minutes or until tender.
Stir in chicken and next 6 ingredients; remove from heat.
Tear tortillas into 1-inch pieces; layer one-third tortilla pieces in bottom of a 13- x 9-inch baking dish coated with cooking spray. Top with one-third chicken mixture and one-third cheese. Repeat layers twice.
Bake at 350° for 30 to 35 minutes or until bubbly.
Note: Freeze casserole up to 1 month, if desired. Thaw in refrigerator overnight, and bake as directed.