The most obvious answer is to add more oats. This can be tricky for this recipe though where you may only realize the issue after removing the dish from the oven. Our first tip is to make sure you are off to the best start by following the recipe closely. Putting it back in the oven could also help the oats to absorb more moisture and thicken the dish. If all else fails, enjoy as is – this recipe is delicious at almost any consistency.