ALately my buttercream has been turning out very grainy and I have no idea why. It almost looks like the ingredients are separating. My recipe is: 1 cup butter 4 cups powered sugar 1 tablespoon vanilla extract 1 - 3 tablespoons milk

Any help would be appreciated!

AWhere are you from? It could be the butter is too soft/warm. Butter melts at 80 degrees and is very temperamental.

AI've been having the same problem! It's mainly my chocolate buttercream that has been grainy and I just can't figure out why. My recipe is very similar to yours.

AI usually only make smbc, but my first thought is if it's grainy, maybe the sugar isn't dissolving. I would try whipping it longer, and maybe increasing your butter by 1-2 tbsp. My second thought is that perhaps you need to sift your powdered sugar?