4 cups frozen mixed berries*, NOT thawed (about 24 ounces frozen fruit)
3 tablespoons granulated sugar
3 tablespoons all purpose flour
zest from 1 lemon
pinch of salt
Oat Crumble Topping
1 cup old fashioned rolled oats
1/2 cup brown sugar
6 tablespoons all purpose flour
1 stick (1/2 cup) salted butter, cold, cut into small cubes
Preheat oven to 350 degrees with the oven in the middle position.
In a mixing bowl, make the berry filling by combining all ingredients and tossing to combine. Set aside.
In a separate mixing bowl, make the oat crumble by combining all ingredients, then use your fingers to pinch the butter and incorporate with the dry ingredients. Keep pinching and tossing together with your hands until evenly combined. You will be left with many pea sized pieces of butter mixed in with the oat mixture. Set aside.
Pour the berry filing into a 1-1/2 quart baking dish (or 8×8 pyrex baking dish, a pie baking dish, or even cast iron skillet). Top with the oat crumble topping, and spread to an even layer.
Bake uncovered until the berry filling is bubbling, and the oat crumble is golden brown, about 1 hour. Let cool for 1 hour before serving. Serve room temperature with ice cream. Will keep covered at room temperature for 3 days.
My favorite frozen berries to use are a combination of raspberries, blueberries and blackberries. I buy a big bag of this frozen triple berry mix and always have it in my freezer. But you could use just 1 berry, or any combination of other berries. For larger fruit/berries like strawberries, cherries, mango, etc I will pulse the frozen fruit in the food processor a few times so the chunks are more bite size
This same recipe also works for fresh fruit too! Just substitute the same amount of fresh berries for frozen.
You can make this up to step 4, then cover tightly and freeze up to 3 months. Bake it fully frozen until golden and bubbling, about 1 hour also.