In a mixing bowl toss the rhubarb, strawberries, 1 cup of the sugar, and cornstarch if you are using it together and pour into a 2 quart baking dish.
In a food processor or mixing bowl combine the flour, baking powder, the remaining ¼ cup sugar, and salt. Add the butter cut in with a knife or pastry blender until the butter is pea sized. Add the oats, milk, and vanilla and stir until just moistened.
Using the cookie dough scoop drop the cobbler topping onto the rhubarb mixture leaving gaps. Bake uncovered for 50 minutes until the rhubarb is cooked and the top is golden brown.