If using frozen berries, measure berries into a colander (fill measurement cup very full) and rinse with warm water to thaw slightly.
Drain for a few minutes and shake colander to remove excess juice. If using fresh berries you can skip step 1 and 2.
Pour berries into a bowl and mix with remaining filling ingredients.
Divide berries among four 1/2 pint jars.
In another bowl, combine topping ingredients. Using a pastry cutter or your hands, mix topping ingredients until it resembles wet sand with oats in it.
Divide topping among the jars, patting it down to fit as much topping in each jar as possible (at least 1/3 cup in each jar; there will be some extra topping).
Screw lids on the jars and freeze.