In my village they are used to call "mix of various kinds of хлопья and dried fruits" мюсли (I believe).
My countrymen prefer something more "substantial" for breakfast : sausages with eggs, cheese, pastries. As Poirot says: "После такого завтрака опять потянет в постель!".
Personally I sometimes have "old-fashioned oatmeal" for breakfast, never cold "хлопья".
Very interesting! Do people ever add milled (or ground) flax seeds to their oatmeal. How would you translate "He mixed ground flax seeds with his oatmeal." into Russian?