These tangy-sweet squares will keep, covered, in the fridge up to 4 days.
To make Filling: Mix 1 Tbs. orange juice and cornstarch in bowl. In pan, combine rhubarb, strawberries, sugar, zest and remaining juice. Bring to a simmer. Reduce heat to low; partially cover, and cook 5 to 8 minutes, or until rhubarb is tender. Add cornstarch mixture, and cook, stirring constantly, until thickened, about 1 minute. Cool.
Preheat oven to 350F. To make Crust and Topping: Combine oats, both flours, sugar, cinnamon, ginger, baking powder and salt in large bowl; blend with fork. Add orange juice and oil; blend with fork until crumbly.
Press 2 cups oat mixture into bottom of 9×9-inch baking pan coated with cooking spray. Spread rhubarb mixture over crust. Stir almonds into remaining oat mixture, and sprinkle over filling. Bake until golden, 30 to 35 minutes. Let cool in pan on rack.