Make the filling. In a large bowl, mix together rhubarb, strawberries, sugar, cornstarch, flour, ginger, lemon zest, and lemon juice. Mix until dry ingredients have dissolved then cover and set aside.
Make the topping. In a large bowl, mix together oats, flour, brown sugar, cinnamon, cloves and salt. Cut in butter until size of small peas.
Prepare a 12-inch camp Dutch oven with a light coat of oil or butter. Pour fruit filling into the bottom of the oven and spread out evenly. Sprinkle toping over the fruit.
Make a circle of 10-11 hot charcoals and place Dutch oven over the coals. Add 16 hot charcoals to the lid, making a circle around the edge. Bake at 375 degrees Fahrenheit for about an hour or until fruit is bubbling up and topping is golden brown