Here’s a Smart Way to Keep That Giant Bag of Costco Onions from Going Bad

Let’s face it, the produce section of a Costco is a calculated risk. The tradeoff for all those super cheap prices is that you have to buy a lot of what you’re getting, and with fresh fruit and vegetables, that’s always a risk. Unless you have a solid game plan, with recipes in place, chances are you won’t make it all the way that three pound bag of broccoli florets before some of them go bad. No, the fruit and vegetable section is not the place for impulse buys.

However, it was ignoring that exact advice (thanks to the twin distractions of two kids and a Saturday crowd), that led me to a discovery that has restored some of my weeknight cooking mojo and streamlined meal prep: I started pre-chopping and freezing my onions.

For me, one of the biggest hurdles to serving weeknight dinners isn’t deciding what recipe to prepare, it is the simple task of prepping the veggies. Many of my favorite dishes, from pasta sauce to soup, start with at least some chopped onions, if not a full mirepoix of carrots and celery. When 6 o’clock hits, the kids are circling and the take-out menu is calling my name. Finding the resolve to start slicing up an onion can feel like the most strenuous task of the day.

Costco sells 10-pound bags of jumbo yellow onions, about twice the size of a standard grocery store bag. When I got it home from the store, I realized: There’s no way we’re going to go through all those. So I set a few onions aside in a basket with my shallots and garlic (for when I want a different sized slice, or need them raw), and I put about half an hour into peeling, chopping, and freezing all of the remaining onions in one fell swoop.

The amazing part? It made that next week’s cooking so much easier. The onions can go straight from the freezer into the pan — they don’t take much longer to start cooking —and the most arduous part of my dinner prep is already taken care of! Plus, I no longer worry about the onions going bad.

Start with your workspace: Get a sharp knife and a cutting board stabilized atop a nonskid mat or damp paper towel. I like plastic cutting boards because they don’t absorb as much odor. (Here’s an easy way to remove odor from any cutting board.)

The sharper the knife, the better: A sharp knife will help keep the tears away. Dull ones crush the onion’s cell walls, which releases more of the sulfur-containing compounds that lead to a mascara-streaked mess. The National Onion Association also recommends chilling the onions for about 30 minutes. When all else fails, invest in a pair of onion goggles.

Once your board is piled high, transfer them to a fine mesh strainer. Rinse under cool, running water. This simple step minimizes the onions’ harsh, raw flavor. Transfer them to a paper-towel-lined baking pan and dry thoroughly before packing in a freezer zip-top bag. Press to remove air from the bag and lay flat to freeze. As long as the onion pieces are dried before freezing it’s easy to remove only the amount you need once frozen. If they are too wet, they’ll turn into onion-flavored ice cubes.

When you’re ready to cook with the frozen onions, massage the bag to separate the chunks of onion. Shake out the what you need for a recipe. One medium bulb yields about a cup of chopped onion. When onions freeze, the water inside the cells expand, puncturing cell walls, and then once the onions thaw or are heated, that moisture escapes. As a result it’s important to remember that these onions will release more water than freshly-diced ones, so be sure to allow extra time for that water to evaporate.