If you really need the taste of a nut milk. I would try Silk brand Cashew milk, unsweetened. It is as all nut milks, heavy in fat, however its lowest in calorie density at only 25 calories per cup. Its similar in creaminess and taste to almond milk but I think lacks some of the bitterness of almond milk. and for those that worry about vitamin deficiencies it does contain this in only a 25 calorie cup:
% of daily needed
B-12 - 50%
Calcium - 45%
Vita D - 25%
Vita -E - 50%
But for the MWL program its not really recommended, but is a better option when trying to transition to better compliance. Ultimately, water is your best choice for oatmeal and if you need it a little thicker just add a TBS of ground flax seed