Wash and slice the peaches.
In a bowl, combine the sliced peaches and the blackberries with 1 tbsp of cinnamon.
Mix to combine and set aside.
In another bowl, combine the flour, sugar, baking powder, and salt and stir to combine.
Stir in the milk and vanilla.
Preheat your Traeger grill to 375*.
Place your cast iron pan in the grill as it heats up.
Add the butter to the pan and allow it to melt.
Once the butter is melted, pour the prepared batter into the pan with the butter.
Place the pan back in the grill and bake for 5 minutes.
Carefully remove the pan from the grill and pour the fruit atop the par-baked batter.
Return the pan to the grill and bake for 30-40 minutes, rotating once.
When the top is golden brown and the batter has puffed up, remove the cobbler from the grill.
Allow it to rest for 5-10 minutes.
Then serve your Traeger baked peach and blackberry cobbler with a scoop of ice cream and enjoy.