Heat oil in nonstick skillet over medium heat. Add onion, carrots and corn, and cook 5 minutes, or until softened. Add turkey and cook 5-7 minutes, or until cooked thoroughly. Add flour and salt, stir to coat. Add Worcestershire, garlic powder, tomato sauce and ½ cup water. Mix well and cook until heated through.
Place cauliflower in large bowl and microwave on HIGH 4 minutes, or until tender. Add cream cheese and ½ cup cheese, and mix with electric hand mixer until smooth.
Spoon turkey mixture into 11x8-inch baking dish. Top with mashed cauliflower and spread to evenly coat. Sprinkle with remaining ½ cup cheese.
Bake 10 minutes, or until bubbly and cheese melts.