I love making my own oatmeal mixture because I know exactly what's in it (many store-bought packets have additives), it's cheaper (every penny counts!), and I think it just tastes better. I keep a large Tupperware of this mixture in my desk at work, along with a 1/4-cup measuring cup; I give the Tupperware a quick shake before measuring out my serving. Alternatively, you could prepackage servings in sandwich-sized Ziplocs. 1/4 cup is about the same amount as the store-bought packets, so that's the serving size the recipe is based on, but I often measure out 1/2 cup portions.