Preheat oven to 325°F.
Prepare a large rimmed baking sheet with parchment paper.
In a large bowl, combine all ingredients. Stir to coat well.
Transfer oatmeal mixture to baking sheet. Spread out into even layer, pressing down to compress the mixture.
Bake for 30-35 mins in oven and cool, untouched for 45 mins.
Break into pieces. Store in airtight container up to two weeks.