If you want to prepare vegetables ahead of time and serve them with a meal on another day, you can saute and freeze them. Sauteing vegetables is an effective way to intensify the flavor, which can be preserved through the freezing process. They won't taste bland when you defrost, cook and serve.
Some vegetables taste better if they're sauteed before freezing. Mushrooms, eggplant, potatoes, zucchini and summer squash are best sauteed, while onions and green peppers may be frozen without any treatment.
When sauteing vegetables for freezing, use olive oil, butter or margarine to bring out the flavors. When they're removed from the freezer, the consistency may be a bit greasy, but reheating will melt the fats and restore the full flavor.
After you saute your vegetables, let them cool prior to packaging in a plastic container or a sealed freezer-safe plastic bag. Cooling keeps the container or bag from trapping heat that will alter the freezing process.
For sauteed zucchini, summer squash and eggplant, it's best to layer the slices with wax paper before freezing. This separates the vegetables so they don't freeze together and break apart when you prepare to reheat them.