If you have space in the freezer, Mediterranean veg freezes ok.
Dice up onions (red are nice), peppers, courgettes, tomatoes (I halve cherry tomatoes), whole or half garlic cloves, etc into the same size dice. (I often add mushrooms, aubergine works well except my family hate aubergine, I’ve added French beans too occasionally).
Season with salt and pepper, dried Med herbs (oregano, basil, thyme, rosemary - those sorts in your own choice of combination), decent slug of olive oil. A dash of balsamic vinegar is also good to add.
Can be frozen before cooking. If you’re careful and freeze spread out enough (so it doesn’t just form a solid lump in the bag), you can take it out in handfuls as needed rather than needing the entire pack.
Leftovers can be frozen after cooking.
Good as a side dish just roasted, add some chopped tomatoes to make a ratatouille, or into a plain tomato sauce to serve with pasta. Or tip passata in a roasting dish and throw veg on top, add some chicken or lamb (and maybe some baby potatoes for total ease of cooking) and do as a tray bake.