In a gallon-size Ziploc freezer bag or other large, sealable container, measure 3 cups oats.
Pour the remaining 1½ cups oats into a food processor with the oat bran*, sugar, and spices. Blend until fine.
Add the coconut oil and vanilla and process until completely mixed in.
Transfer the ground oat mixture to the bag with the oats. Seal tightly, leaving a little air in the bag, and shake well to combine.
Store in the freezer in the large bag, to scoop later. Alternately, divide into individual ⅓-cup size portions and store in the pantry.
To serve: add ⅓ cup water to ⅓ cup instant oatmeal (or measure anywhere from ¼ cup to ½ cup oats and an equal amount of water, depending on how large a serving you would like). Stir to combine and microwave for 45-60 seconds.
The mixture should be very thick. Thin with milk as desired and serve hot.