Yes, you can freeze oat milk, and it can last for up to 6 months past the expiration date. However, the longer it stays frozen, the more likely It is for its texture to change. The ingredients begin to settle, resulting in grainy milk. When storing oat milk, please keep it in the back of your freezer and away from any heat sources, light, and smelly food. Furthermore, transfer it to another airtight container. Water is the main ingredient and will expand while freezing, so the packaging may explode. There should be an inch of extra room in your container, as milk expands if frozen.