In a small bowl, combine the ground flaxseed and water. Stir well and let it sit for about 5 minutes until it thickens. This will be your egg substitute.
In a large mixing bowl, add the peanut butter, pure maple syrup, and vanilla extract (if using). Stir until well combined and creamy.
Once the flax egg has thickened, add it to the peanut butter mixture and mix until fully incorporated.
In a separate bowl, whisk together the quick oats, baking soda, ground cinnamon, and sea salt.
Gradually add the dry ingredient mixture to the wet ingredients, stirring until just combined. Be careful not to overmix. Fold in the vegan chocolate chips.
Using a tablespoon or cookie scoop, drop the cookie dough onto a prepared baking sheet lined with parchment paper. Leave enough space between each cookie as they will spread slightly while baking.
Preheat your oven to 350°F (175°C) and bake the cookies for 10-12 minutes, or until the edges are lightly golden.
Once baked, remove the cookies from the oven and allow them to cool on the baking sheet for about 5 minutes before transferring them to a cooling rack. Enjoy your Vegan Oatmeal Peanut Butter Chocolate Chip Cookies warm or at room temperature!