Preheat the oven to 350. Spray a 9x13 baking dish.
Toss the rhubarb and strawberries in the baking dish.
In a mixing bowl, whisk together the remaining ingredients, except the brown sugar. Pour the batter over top of the fruit and stir gently to combine the fruit.
Sprinkle the brown sugar over the top.
Bake in the preheated oven for 25 to 30 minutes, or until toothpick comes out clean in the middle.
Serve Strawberry Rhubarb Baked Oatmeal with milk, cream, yogurt (or even with ice cream as a dessert!).