- Preheat the oven to 375 F. Lightly coat a 9-inch pie pan with cooking spray.
- Arrange peach slices in the prepared pie plate. Sprinkle with lemon juice, cinnamon and nutmeg.
- In a small bowl, whisk together flour and brown sugar. With your fingers, crumble the margarine into the flour-sugar mixture.
- Add the oats and stir to mix evenly. Sprinkle the flour mixture on top of the peaches.
- Bake until peaches are soft and the topping is browned, about 30 minutes. Cut into 8 even slices and serve warm.