I started making oatmeal about the same time that I started using almond milk. Even when I was still drinking cow's milk, I was making my oatmeal with just water. Because of this, I never really developed a need to use dairy in my oatmeal (as you can see from my recipes).
However, I can understand why some people might have an acquired taste for oatmeal made with dairy. Of course, I highly recommend using nondairy milks, as a personal preference, but here are some tips for mimicking the taste of dairy products in your nondairy porridge!
1. Add extra salt.
Because it happens so rarely, when I do have oatmeal made with cow's milk, the first thing I notice is how salty it is. Adding a little extra salt to your nondairy oatmeal can give it a milky, buttery taste. Don't go overboard, obviously; I wouldn't go over 1/8 of a teaspoon per serving!
2. Use coconut oil.
Coconut oil adds a certain richness to your porridge. It's not as flavorful as butter, for example, but it definitely adds a butter-like quality!
3. Stir in nondairy yogurt.
If you add a few spoonfuls of nondairy yogurt (I like almond or coconut-based yogurts), it will make your oatmeal extra creamy, but without the tang of actual yogurt, so it tastes as if you just stirred in heavy cream! I like the plain or vanilla varieties. Also, this is how I flavored my Coconut Cream Pie Oatmeal (below).
4. Earth Balance
Okay, this one is kind of cheating. It tastes exactly like butter. :) But if you're hooked on the taste of butter in your porridge, this might be your key to transitioning! I personally never got in the habit of "buttered oatmeal," but I understand the appeal; I personally grew up on Cream of Wheat with butter, sugar, and cinnamon! Mmmm...nostalgia.
5. Opt for flavorful oatmeal recipes.
Your best bet might be to steer clear of the simpler recipes. For example, if you were comparing a basic bowl of oatmeal made with cow's milk to a basic bowl with almond milk, you would absolutely notice the difference. On the other hand, if you were comparing two bowls of Almond Joy Oatmeal or Chocolate Strawberry Oatmeal (shown below), would wouldn't notice (or at least mind) the difference. The more seasoned or flavored the recipe is, the less of a role the dairy will play!