Preheat the oven to 350F.
Butter a 9x9 baking dish.
Drain the pie cherries, reserving at least 1/2 cup of the liquid.
Mix the 1/2 cup cherry juice with the tapioca and let sit while you get everything else ready.
Melt the 1/2 cup butter in a saucepan or in the microwave, then mix it with the brown sugar, oatmeal, flour, baking powder, salt and baking soda.
Put half the oatmeal mix in the buttered baking dish and pat out until the bottom is covered.
Pour the cherries and tapioca and cherry juice into the dish and spread out.
Top with the rest of the oatmeal mix.
Bake 30-35 minutes.
Great warm and good at room temperature as well.