Preheat oven to 375 degrees. Grease an oven-safe dish (pie pan or medium size casserole dish) with a little butter.
Toss rhubarb chunks with sugar.
Mix whole wheat flour, oats, brown sugar (or honey), soft butter, and seasonings with your fingers or a fork.
Spread this mixture over rhubarb in baking pan.
Bake for 30-40 minutes until bubbly and lightly brown.