Preheat oven to 350 degrees F. Grease an 8x8 inch glass or metal baking dish.
In a large bowl, whisk together the oats, flaxseed, brown sugar, salt, baking powder and cinnamon.
In a separate bowl, whisk together melted butter, eggs and milk.
Pour the wet ingredients into the dry ones and stir until combined well. Gently stir in the walnuts, apples and raisins.
Pour batter into baking dish. Bake for 20-25 minutes or until an inserted toothpick comes out clean. Serve with warm milk and a bit more brown sugar on top, if desired.
FREEZER MEAL INSTRUCTIONS:
To freeze: Complete recipe through step 4. DO NOT BAKE before freezing. Wrap casserole dish tightly in a few layers of plastic wrap and one of foil and place in the freezer.
To prepare: Thaw in the fridge for 24 hours and bake according to directions. Or defrost in the microwave and bake. If baking from frozen, cover oatmeal with foil and plan to bake longer, until the middle is cooked through.