Heat oven to 350°.
Lightly grease baking dish with oil or butter.
In a large bowl, whisk the eggs to combine them.
Stir in the remaining ingredients, except the apples and walnuts. Stir to combine.
Fold in the apples and walnuts.
Pour oatmeal batter into prepared 9X13 baking dish.
If garnishing, arrange apple slices around the top and add additional walnuts plus a sprinkling of cinnamon.
Bake for 40 minutes.
Serve with milk as is, or with an additional drizzle of syrup and walnuts.