Preheat the oven to 400 degrees F and place a rack in the center of the oven.
Place the berries in a 12-inch high-sided skillet or braiser set over medium heat. Stir in 1 tablespoon of the flour, 1/4 cup of the sugar, 1/4 teaspoon of the cinnamon and the lemon juice. Cook until all the juices release, 5 minutes.
To make the crumble topping, in a medium bowl combine the oats, peanut butter, brown sugar, the remaining 1/4 cup granulated sugar and the remaining 3/4 cup flour. Mix with a spoon until combined. Pour the butter into the dry crumble mixture and stir to achieve a crumble consistency. Spoon dollops of the crumble mixture over the berry mixture. Bake until the topping is crisp, 20 minutes. Cool the crumble for 5 minutes, then serve.