Pre-heat the oven to 400F
Chop peaches in to bite sized pieces and toss with 3 tbsps brown sugar. Set aside.
Mix together the flour, oats, remaining ½ cup brown sugar, and salt in a large bowl.
Add the vegan butter or coconut oil and mix with a spatula or your hands until the dough becomes crumbly but combined.
Add the agave syrup and mix once more.
Set 1 cup of the crumble mixture aside in a separate bowl.
Firmly press the remaining mixture in to a 8x8 parchment lined baking dish.
Pour the peaches on top of the crust and spread them out evenly.
Crumble the rest of the oat mixture evenly over the peaches until all the dough is gone.
Bake for 35-45 minutes or until the top is golden brown and crisp.
After the crumble bars have been baked, let cool in pan for about 15-20.
In a small bowl mix together the powdered sugar, non-dairy milk, and vanilla to make a glaze. Drizzle the glaze over the bars and serve!