Preheat oven to 375 degrees F (190 degrees C).
Chop the Almonds (1/2 cup).
Put the Frozen Mixed Berries (3 cup) in a large bowl and coat with Corn Starch (1 tablespoon), a third of the Salt (1/4 teaspoon), white Granulated Sugar (1/2 cup) and Lemon Juice (1 tablespoon).
Cream Unsalted Butter (6 tablespoon) and Brown Sugar (1/3 cup) with a fork. Incorporate Old Fashioned Rolled Oats (1/2 cup), All-Purpose Flour (3/4 cup), remaining Salt (1/2 teaspoon), almonds, and Baking Powder (1/2 teaspoon) with fingertips.
Lightly grease an 8 inch baking pan and put the berry-mixture in. Top with the oat-mixture.
Bake for 50 to 60 minutes. Let cool on a wire rack. Enjoy warm or at room temperature!