Preheat oven to 350°F (175°C).

Butter a shallow 1 1/2 qt baking dish.

In the baking dish, combine cooked brown rice, peaches (fresh or drained canned), and 1/3 cup of brown sugar.

In a separate bowl, mix together the flour (whole wheat or all-purpose), remaining brown sugar, cinnamon, and nutmeg.

Cut in the margarine (or butter) into the flour mixture until it becomes crumbly.

Sprinkle the crumbly mixture evenly over the peach and rice mixture in the baking dish.

Sprinkle the chopped walnuts or pecans over the flour mixture.

Bake in the preheated oven for 20-25 minutes, or until the topping is golden brown and the peaches are bubbly.

Let stand for a few minutes before serving.

Serve warm.