Stir the vanilla and brown sugar into the cold water until dissolved.
Add the oats, salt, and water mixture to a blender. Blend on high for 30 seconds.
Pour the blended oat mixture through a strainer like a nut bag, cheese cloth, metal coffee filter, or a double layer of metal sieves to filter out the oat pieces.
Chill the oat milk completely (preferably overnight), then shake very well before serving. Keep the oat milk refrigerated for up to four days.
*You can use any type of sweetener that dissolves easily in cold water.**There is no nutritional information for this recipe because nutritional calculators can not account for the oats that are discarded in the straining process.