I found the original recipe on the King Arthur Flour website. I say original because I modified it a bit. To my tastebuds the K.A.F. recipe is way too sweet, uses way to much spice and is too dry. On the plus side it uses no flour and no eggs (my Baked Oatmeal research uncovered recipes that use both - that is way too close to muffin territory).
Julie's Apple Cinnamon Baked Oatmeal Recipe
PREP 5 to 15 mins. CHILL overnight. BAKE 45 mins. to 50 mins. YIELD 9 to 12 servings.
I've experimented with a couple of flavor variations and love them all. I like the nuts whole for the texture.
+Cranberries (fresh or frozen), maple syrup, walnuts, nutmeg
+Tart cherries, honey, almonds, lemon or orange zest
+Apples, maple syrup, pecans, cardamom
2 cups rolled oats
1/2 cup steel-cut oats
2 tablespoons golden flax meal, optional
½ teaspoon cinnamon
½ teaspoon salt
2 ⅔ cups milk (dairy, almond, soy, coconut, etc).
1/4 cup boiled cider*
1/2 cup applesauce**
2 tablespoons unsalted butter, melted
1 teaspoon vanilla extract
2 medium baking apples***, peeled, cored, and cut into 1/2" cubes (about 2 1/2 cups)
3/4 cup walnuts or pecans, chopped or whole
1. Lightly oil an 8" or 9" square baking dish. (9"x5" loaf pan for a half recipe).
2. In a large bowl, combine the oats, flax, sugar, cinnamon, and salt. Set aside.
3. In a separate bowl or large measuring cup, mix together the milk, boiled cider, applesauce, melted butter, and vanilla.
4. Stir the wet ingredients into the dry until evenly moistened. Stir in the apple cubes and nuts.
5. Spoon the oatmeal mixture into the prepared pan, spreading it into an even layer.
6. Cover the pan with plastic and refrigerate the oatmeal overnight.
7. Next morning, preheat the oven to 350°.
8. Bake the oatmeal for 55 to 65 minutes, until the edges are bubbly; the center might appear slightly wet.
9. Remove the oatmeal from the oven, and allow it to cool for 5 to 10 minutes before serving.
Store baked oatmeal in the refrigerator and reheat individual servings with a little water or milk in a microwave or over a burner.
* ¾ cup fresh apple cider simmered till reduced to ¼ cup
** don't skip the applesauce, make your own, skip the sugar
***If you can find them, Macoun taste great and hold their shape