Rhubarb Oatmeal Bars

1 1/2 cup flour, un-sifted
1 1/2 cup old-fashioned rolled oats
1 cup brown sugar, firmly packed
1/2 teaspoon cinnamon
1/4 teaspoon salt
3/4 cup butter, softened
3 cups rhubarb sauce (recipe follow), thickened
1/4 cup walnuts, chopped

Heat oven to 375 degrees. Lightly grease 13 x 9" pan. Combine first 5 ingredients. Add butter, stir with fork until mixture resembles coarse crumbs. Press half of crumb mixture into bottom of pan. Spread rhubarb sauce evenly onto crumb layer. Top with remaining crumbs and chopped walnuts. Bake 25 to 30 minutes or until top is golden brown and rhubarb is bubbly. Cool to room temperature before cutting.