Preheat oven to 350°F (175°C).

Combine oats, 1 cup flour, and brown sugar in a large bowl.

Cut in margarine with a pastry blender until the mixture resembles coarse meal.

Press one-half of the oat mixture into the bottom of a 9-inch square pan coated with cooking spray.

Bake at 350°F (175°C) for 15 minutes.

Remove from oven and sprinkle chopped walnuts over the prepared crust.

Combine caramel syrup and the remaining 1/4 cup flour; stir well.

Pour the caramel syrup mixture over the nuts.

Sprinkle the remaining oat mixture over the syrup mixture.

Bake at 350°F (175°C) for 25 to 30 minutes, or until golden brown.

Let cool in pan on a wire rack.

Cover and chill for at least 1 hour.

Cut into bars to serve.