Step 1

Preheat oven to 375 degrees F (190 degrees C). Grease a 2-quart baking dish.

Step 2

Combine rhubarb, strawberries, white sugar, lemon juice, and lemon zest together in a bowl.

Step 3

Stir brown sugar, whole wheat flour, oats, salt, and cinnamon together in a bowl. Cut cold butter into oat mixture with a pastry blender until the mixture resembles coarse crumbs and butter pieces are pea-sized.

Step 4

Pour rhubarb mixture into prepared baking dish. Spread oatmeal mixture evenly over the top.

Step 5

Bake in the preheated oven until golden and bubbling, about 35 minutes.