Low-hanging fruit: I increased my average intake of vegetables with minimal effort by acquiring microwaveable frozen vegetable bags, which have become my default "I want to eat something but don't want to spend effort preparing it" food. Each bag can be transferred directly from freezer to microwave and takes an average of five minutes therein, and then you cut open the bag and transfer to a serving dish (or, like me, just plop the open bag into a plastic tray and eat directly from it).

It's not perfect (for example, I cannot find green leafy vegetables in this packaging - then again, given the texture of frozen chopped spinach I probably wouldn't want to), but it's an improvement over most other foods that take similar amounts of preparation.