Canning with oil is an old method of preserving food. There are three ways to preserve with oil.
Once you can put the vegetables raw or cooked floating in oil. Another option is to chop up the veggies and other ingredients and mix them with oil (basil pesto). You can also pickle dried vegetables in oil (dried tomatoes in oil).
Spices can also be preserved in oil to flavor the oil (garlic and chili oil).