Heat oil in a medium skillet over medium heat; saute onion, green bell pepper and red bell pepper until tender. Remove from heat and stir chicken into skillet, then add soup and milk and mix well.
Spread 1 cup rice in the bottom of a lightly greased 9x13 inch baking dish, then layer with chicken mixture, remaining 1 cup rice and top with cheese.
Bake at 375 degrees F (190 degrees C) for about 30 minutes, or until heated through and cheese is melted. Serve with heated flour tortillas, fajita style.
