Preheat the oven to 350°F and prepare a 9x13 baking dish. Set aside.
Combine frozen peaches, sugar and lemon juice in a medium saucepan. Cook on medium-low heat, stirring often, about 8 minutes, until peaches have softened.
Mix the arrowroot or cornstarch into the peaches and cook for another 3-5 minutes, bringing to a simmer. Then, turn off the heat & set aside.
Place the butter cubes into the baking dish and place in the oven for 2-4 minutes or until butter is completely melted. Remove from and allow to cool slightly.
Meanwhile, in a large bowl whisk together the sugar, vanilla, gluten free flour, baking powder, and salt. Then, whisk in the oat milk until a thick batter is formed.
Pour the batter into the pan of melted butter and carefully spread into an even layer. Don’t stir the batter with the butter!
Use a spoon to carefully place the cooked peaches over the batter so they’re spread out evenly across the pan.
Bake for 35-40 minutes or until golden brown. Allow to cool at least 30 minutes to allow the butter to soak into the cakey parts of the cobbler.
Serve with vanilla ice cream & enjoy!