• Preheat oven to 350°F. Grease a 9 x 5-inch loaf pan and line it with parchment paper, leaving an overhang in at least one direction for easy removal.
• Peel and core the apples, then chop them into ¾-inch pieces.
• Toss with granulated sugar, cinnamon, and nutmeg, and set aside. The apples will become slightly syrupy as the sugar draws out moisture.
• In a large bowl, mix together the flour, granulated sugar, baking powder, and salt.
• Create a well in the center, then add the oat milk, oil, and vanilla extract. Stir until smooth and well combined.
• In a small bowl, mix together the light brown sugar, flour, and cinnamon.
• Add the oil and water, then use your fingers or a fork to combine until small clumps form.

Assembly

• Pour ⅓ of the batter into the prepared loaf pan and spread evenly.
• Layer with half of the chopped apples.
• Add another ⅓ of the batter and spread to cover the apples.
• Add most of the remaining apples (reserving a few for the top layer) and cover with the rest of the batter.
• Scatter the reserved apples on top and sprinkle evenly with the crumble.
• Bake for 50-60 minutes, until the edges are golden brown, and a skewer inserted in the center comes out clean.
• Let the loaf cool in the pan for at least 20 minutes before transferring it to a cooling rack.
• Best enjoyed the same day. If storing, place in an airtight container and refrigerate for up to 3 days. Bring to room temperature before serving or toast slices in the oven to re-crisp the crumble topping.