Preheat the oven to 350 degrees F (180 degrees C). Line 2 baking sheets with parchment paper.
Add the vegan butter, peanut butter, and brown sugar to a large mixing bowl. Beat with a wooden spoon until smooth and creamy.
Pour in the almond milk and vanilla extract. Beat to combine.
In another mixing bowl, whisk the flour, xanthan gum, baking soda and salt until well combined. Sieve the flour mixture into the bowl with the wet ingredients.
Fold everything together until just combined.
Add the rolled oats, and fold again to combine.
Roll the cookie dough into balls, and place on lined baking sheets. Leave enough space between each dough ball to allow for spreading.
Using the bottom of a glass, gently push each dough ball to flatten slightly. Bake for 10 to 12 minutes.
Leave cookies on a baking sheet for 5 to 10 minutes before using a spatula to move them to a wire rack to cool.