French stews often take a long time to cook to ensure that the meat is properly tender. That doesn't always bode well for the vegetables in the stew. The key to success is cooking in phases and learning when to add each type of vegetable for best results. Of course, the size of your vegetables and the way you cut them play a part, but this is a good general guide for when to add different vegetables to your stew.
Because these vegetables are the most dense, they’ll need the longest time to cook through. Saute them with your aromatics at the start to create a flavorful base for your stew.
Onions
Carrots
Leeks
Turnips
Fennel
Potatoes
These are vegetables that require about 10-20 minutes of simmering in your stew to become tender.
Cabbage
Green beans
Mushrooms
Due to their small size and/or high water content, these are quick cooking vegetables that only need a few minutes. Throw these into your stew when you’re just about ready to serve.
Peas
Leafy greens
Zucchini/Squash
Corn