PREHEAT oven to 400°F. Heat oil in large skillet on medium-high heat. Add chicken; cook and stir until cooked through. Drain. Add green pepper, seasoning mix and water. Bring to boil. Reduce heat to medium-low; simmer 10 minutes, stirring occasionally.
SPOON chicken mixture into 9-inch pie plate; sprinkle with cheese. Prepare muffin mix as directed on package; spoon over cheese, completely covering cheese layer.
BAKE 20 minutes or until golden brown. Let stand 5 minutes before serving.