Preparation

• Fit pastry into a 9-inch deep dish pie plate and refrigerate until ready to use.
• Preheat oven to 400℉.
• Mix old fashioned oats, all-purpose flour, and light brown sugar in a medium mixing bowl. Cut in butter until it forms coarse crumbs. Set aside.
• In a large mixing bowl, stir together granulated sugar, cornstarch, ground cinnamon, and grated nutmeg.
• Add sour cream and egg, stirring until combined.
• Stir in rhubarb. Transfer to prepared crust.
• Top with oat mixture and put pie plate on another baking sheet to catch any potential drips.
• Bake in the lower ⅓ of the oven for 15 minutes. Reduce the heat to 350℉ and continue to bake until the top is golden brown, about 35-40 more minutes.
• Cool to room temperature then chill. Store leftovers in the refrigerator.