Preheat oven to 375°F (190°C). Grease and lightly flour a 9x13 inch baking pan.
In a large bowl, combine flour, oats, brown sugar, baking soda, and salt. Cut in cold butter using a pastry blender or your fingers until mixture resembles coarse crumbs.
Press half of the crumb mixture into the prepared pan. Bake for 10 minutes.
While the crust is baking, in a separate bowl, combine peaches, sugar, cornstarch, lemon juice, and cinnamon.
Pour peach mixture over the pre-baked crust. Sprinkle the remaining crumb mixture over the peaches.
Bake for 30 minutes, or until golden brown and the filling is bubbly.
Let cool completely before cutting into bars.
Notes
Serve warm or at room temperature. Store leftovers in an airtight container in the refrigerator.