– 1 (9-inch) unbaked pie crust – forms the buttery, flaky bottom that holds the filling without sogginess

– 6-8 medium Granny Smith apples (about 8 cups sliced) – tart flavor holds shape during baking, balancing sweet topping

– 3/4 cup granulated sugar – sweetens apples and draws out juices for syrupy filling

– 2 tablespoons lemon juice – brightens tartness and prevents browning

– 2 teaspoons ground cinnamon – adds warm spice essential for apple filling

– 1/4 teaspoon ground nutmeg – subtle depth that complements cinnamon

– 2 tablespoons all-purpose flour – thickens juices to avoid runny pie

– 1 cup all-purpose flour – base for crumbly texture

– 1/2 cup packed brown sugar – caramel richness and chew

– 1/2 cup cold unsalted butter, cubed – creates flaky, melt-in-mouth bits

– 1/2 cup old-fashioned oats – boosts crunch without sogginess

– 1 teaspoon ground cinnamon – ties topping to filling flavors