Preheat oven to 350 degrees and grease a 9 inch circle baking pan. In a large bowl, combine rhubarb, strawberries, sugar, and 1/3 cup flour. Transfer to prepared baking pan.
In another mixing bowl, mix together remaining flour, brown sugar, oats, cinnamon, and nutmeg. Use clean fingers to incorporate the butter into the flour mixture until it has the consistency of course cornmeal. Sprinkle mixture over strawberry-rhubarb mixture making sure to cover the entire top.
Place pan on a baking sheet (in case anything boils over) and bake for 30-35 minutes or until the sides are bubbling and the top is browned.
Serve warm with ice cream.