Preheat oven to 400°. Mix oats, baking powder and cinnamon. In another bowl, whisk eggs, milk, brown sugar and oil until blended; stir into oat mixture. Fold in apple, cranberries and walnuts., Transfer to a greased 13x9-in. baking dish. Bake, uncovered, until set and edges are lightly browned, 35-40 minutes. Slice; serve with milk., Freeze option: Freeze cooled individual pieces on waxed paper-lined baking sheets until firm. Transfer to airtight freezer containers; return to freezer. To use, microwave each piece on high until heated through, 1-2 minutes.