Preheat oven to 375 degrees.
Quarter and cut the apples into slices. You don't have to peel them unless you prefer to avoid the skins. Place apple pieces in a pie plate or shallow baking dish.
Mix pumpkin pie spice and cornstarch together in a small bowl. Sprinkle pumpkin pie spice-cornstarch mixture over apples, and toss lightly.
Microwave apples for approximately 3 minutes on high, or until they are slightly softened. Sprinkle cranberries over cooked apples.
While apples are cooking, place oats, walnuts, brown sugar, and butter in the bowl of a food processor and pulse about 15 times until mixture is well combined and resembles damp sand.
Mix the pumpkin seeds into the oat mixure by hand.
Sprinkle oat, nut, seed mixture over apples and cranberries.
Bake 12-15 minutes or until apples are bubbly and tender, and topping is golden.
Serve warm, with a scoop of vanilla ice cream, whipped cream, or vanilla yogurt if desired.