Preheat oven to 250 degrees F. Coat a 9 x 9 inch silicone baking pan with cooking spray. If using a 9 x 9 inch metal baking pan, coat with cooking spray. Line with parchment paper letting the the side edges overhang by 2 inches. Coat the parchment paper with cooking spray. Set aside.

In a large bowl, add the rolled oats, chocolate chips, peanuts, peanut butter, sweetened condensed milk and cinnamon. Stir until the ingredients are will combined.

Spread the oat mixture into the prepared pan. Press down so that the top is smooth and evenly fills the pan.

Bake for 45 to 50 minutes. The bars should be set and light brown on the edges.

Remove from the pan from the oven and place on a cooling rack. Let the bars cool in the pan for at least 1 hour.

If using a silicone pan, flip over onto a cooling rack. If using a metal baking pan, use the parchment paper to lift the bars from the pan and flip over on a cooling rack. You want the bottom side of the bars facing up. If the bottom of the bars is sticky, let air dry for about an hour or so.

Cut into 16 bars. Store in an airtight container or wrap individually in cellophane bags. Store at room temperature for up to a week or in the freezer for up to 2 months.