General Mills has a sorting system to filter gluten from their raw oats
In contrast to Quaker, General Mills incorporated a sorting process to filter out gluten contaminant in their supply of raw oats. This process is intended to sort the oats below their 20 ppm of allowable gluten. And, because the oats are also ground into flour, there is no risk for stray particles of wheat, rye, and barley to make it through their serving.
After grinding, the oat flour is thoroughly mixed into a homogeneous substance and is mixed further to become the raw material for making cheerios.