Heating up an entire oven takes a fair amount of energy, and it can feel a little wasteful to use all of it to heat a single foodstuff (whether a Party Pizza or a small pork loin). But, as anyone who has ever used an oven knows, ovens stay hot and toasty even after they’re switched off — such is the miracle of thermodynamics — so you might as well put that heat to work.
Let’s say, for instance, that you have purchased (or baked) a lovely baguette to eat with your oven-cooked supper, but all of your butter is (tragically) fridge-cold and hard. Put the butter in a rimmed dish, set the dish on the warm oven, and let it sit and soften while you set the table. (How quickly it softens will depend on how hot you had that thing running, so use your best judgment.) If your bread is a bit stale, do not fret; residual heat can also be used to crisp up a loaf of bread that’s a day or two old (run it under water first it it’s really stale).
If a good bit of time has passed and most of the heat has already seeped from your oven, you can elevate your cheese course by using the last bit of lingering warmth to bring a fancy cheese to room temperature. (Room temp cheese tastes much better than cold cheese.) You can also toss bread dough in there and use it as a proofing drawer — but only after it’s cooled down significantly; you want it warm — between 75 and 95ºF — not hot.
I find a still-warm oven to be especially helpful in the morning. I’ll often keep my bacon in the oven after I’ve turned it off to keep it hot, and I’ll toss the toast in there to keep it, well, toasty, until the eggs are ready. (I always cook the eggs last, since they cook quickly and must be served piping hot.) If you’re oven wasn’t set too high to begin with, you can even use it as a plate warmer. Nothing ruins a hot egg quite like a chilly plate.