I actually cook all my veggies for the week all at once and then save them in the fridge, so they're all pre-cooked before I add them to the skillet. Saves a lot of the fiddly trial-and-error checking to see if my carrots are done at the same time as my broccoli or whatever.

Except onions, garlic, and chili flakes. Those get cooked in the oil before I add all the other veggies.