We wondered if oats might work just as well as sandwich bread as a thickener in soups.
Many pureed soup recipes call for sliced white sandwich bread as a thickener. Since we don’t always have sandwich bread on hand, we wondered if oats might work just as well. We made three of our soups that we thicken with bread—potato-leek, creamy tomato, and Italian garlic soup—subbing in 1/2 cup of oats for each slice of bread called for in the recipe. The oats worked well in the potato and garlic soups, but tasters found that they dulled the bright flavor of the tomato soup and created a slightly gelatinous consistency. We fixed both issues simply by reducing the amount of oats by half.
In sum: Whole oats can be used instead of bread to thicken soup. (Quick oats work fine, too.) Use 1/2 cup oats per slice of bread for most soups. For tomato-based soups, only use 1/4 cup oats per slice.