Look, I will be the first to admit that I've done a bit of microwave bashing in my day. However, a new study has come along and managed to make me eat my words . . . and my veggies. Here's why: in the study researchers found that on the whole, microwaving vegetables and fruits as a means to cook them was the least destructive to nutrients like vitamin C compared to other methods (aside from steaming). This is mainly because cooking methods like baking and grilling exposes foods to higher temperatures and more cooking time, which is destructive to nutrients.
However, go easy on the water because whenever vegetables are immersed in cooking liquid, water-soluble nutrients seep out of the food and into the surrounding liquid, which is why boiling them is not the best option either. To keep the nutrients intact when microwaving, you need only a couple of tablespoons of water to cook raw vegetables. The frozen ones need no extra liquid at all.