How To Grill Onions On Grill In Foil [Everything You Need to Know]

Onions. You can slice them, dice them, and put them on the grill. Few things can smell as delicious as frying onions, so much so that the smell is often used to sell houses. Grilling them in foil can be a great way to make perfect onions, but how can you do it right?

Grilling onions in foil on the grill is very easy and doesn’t require much skill. Adjust the grill to medium heat to ensure the onions don’t burn and have all the time they need to sweeten up and caramelize to perfection. Grilled onions are the perfect condiment to accompany any dish.

how to grill onions on the grill in foil

An onion is one of those versatile foods great in just about any cuisine. However, with its robust flavor profile, this vegetable changes once you start to sweat it down. Suddenly it transforms from the insanely strong vegetable it was to be sweet and tender and even beyond, into caramelized perfection. 

Here’s how you can grill the perfect onions in foil.

How Do You Grill Onions?

Grilling onions is very easy and not complicated at all. However, it is best not to put whole onions directly on the coals since this will cause them to burn rather than become tender and caramelized.

Take the time to prepare a foil packet. Enclose the onion in this packet before placing it on the grill. 

Importantly, as some have found out too late, you should not put the onions directly on the grill’s heat source. Onions can’t withstand that level of heat. So instead, place your foil-covered onions on the grill itself. 

Your onions should be done in approximately 25 minutes, and there’s no need to turn the foil parcel over during the grilling time.

Which Side Of The Foil, Dull Or Shiny?

The question of “dull side or shiny side out” has been the topic of arguments and controversial conversations for many years. 

Home cooks and barbecue enthusiasts have taken a stance that they are willing to defend with all they have. But now, thanks to science, we can finally confirm which viewpoint is the right one.

And the scientific answer is…

It honestly doesn’t matter. Your food won’t get poisoned, or whatever old wives’ tales you’ve been told about how to use your foil and why. Neither will it make a difference in the cooking time or juiciness of your onions.

The fact is that there is a shiny and dull side to the foil. This is simply because of how it is manufactured. 

The dull side is only dull because of a heating process from the machine and nothing else. There are no poisonous particles on the dull side that will affect your food or its taste.

How To Fold A Foil Packet?

Folding a foil packet is not complicated at all; as we now know, it doesn’t matter which side of the foil you use. There are two ways to fold a foil parcel for grilling onions:

Foil Packet Option 1

  • Prepare the foil for the foil packet. The size should be approximately 18 x 12 inches. Place it so that the long side (18 inches) runs vertically.
  • Prepare the onions. You can have them sliced, diced, or whole, whichever you prefer. 
  • Place the onions on the foil. Be sure to use a lob of butter, or coat the onion with a little oil. This is also where you should add salt and pepper and any other spices you like to add to your food.
  • Bring the top and bottom sides of the foil together. This is the longer side (18 inches) of the foil rectangle you prepared.
  • Once you have these two sides together, start to fold them towards the onions. Do not fold It too tightly; you should give the onions some air to breathe.
  • Lastly, tuck in the side of the foil parcel (again, take care not to fold it in too tightly, leaving some space for air and steam to do their magic with the onions).

Foil Packet Option 2

  • With this option, you start by preparing your rectangle of foil as with the previous method, but then you fold the foil over by tucking it in the bottom and top sides of the 18-inch strip. Make a tight seal on top. (This is to be done before you add your onions.)
  • Now tuck in one of the sides, closing it securely.
  • You can now put the prepared onions into the foil packet with the butter or oil and your preferred seasoning.
  • Finally, tuck in the last side that was still open, keeping in mind that there should be some air in the foil packet. This allows for a build-up of steam, which in turn helps to tenderize the onions.

What Temperature Should The Grill Be?

Prepare the grill for indirect heat, which means that the grill shouldn’t be too hot for the onions. Most grills, such as pellet grills, utilize a flame broiler to ensure you’re cooking on indirect heat. So you’ll want to understand how your grill works. 

The perfect temperature for grilling onions is medium heat (a temperature of 350°F). You will know that your grill has reached the correct temperature if you can keep your hand over the grill for six to seven seconds without any extreme discomfort.

With this temperature, your onions won’t end up burned. Instead, they will be sweet and tender in approximately 35 minutes.

Can Onions Be Grilled Without Aluminum Foil?

Maybe you ran out of aluminum foil and haven’t been to the store? Or, maybe you’re trying to avoid using foil because of health concerns (although, as we now know, there is no need to worry about that).

If this is the case, don’t despair; you can grill your onions without foil. The key is not to let them fall through the grill grates.

Below are some other options you can use to grill onions at home:

Grill Pan: A grill pan is similar to a frying pan but has ridges that allow the fats and juices to drain away from the food. It’s the perfect tool for grilling onions without foil because it keeps them from falling through the grill grates. If you’re trying to caramelize the onions, use thick-bottomed, stainless steel, or cast iron pan.

Skewers: Another option is to use skewers when grilling onions. Ensure you slice the onions in wedges. Then pierce the onions with the skewer, making sure to go through the center of the onion so that it doesn’t fall apart while cooking. 

If using wooden bamboo skewers, soaking them for 20 minutes before cooking ensures they won’t burn on the grill. 

Grill Mat: The last option is to invest in a silicone mat that you can place on top of the grill grates. This will provide a flat surface for the onions and prevent them from falling through the grill. The downside to using a mat is it will prevent the onions from getting those nice grill marks.

Grilling Basket: Grilling baskets are high-sided perforated pans with holes, making it easier to cook smaller foods without falling out. Slice the onions to your liking and place them in the basket. Then place the basket on the grill and close the lid.

Whichever method you choose, be sure to brush the onions with oil before cooking to help prevent them from sticking.

How Long To Grill Onions?

As a general rule of thumb, it takes approximately 10-20 minutes to cook one-inch thick slices of onion on a medium-heat grill (350°F). That said, every grill is different, and the cooking time will vary depending on the size of the onion, ambient temperature, and preference.

It’s essential to keep an eye on the onions. Instead of using a thermometer, grab a pair of tongs and turn them over 1-2 times to ensure they cook evenly. This will also help you to get a feel for how long they will take to cook.

Also, some people prefer to eat onions that are cooked longer, so they are more tender. So, if you like your onions on the softer side, cook them for a little longer.

On the other hand, if you prefer your onions to have a bit more crunch, don’t cook them too long. 

How To Know When The Onions Are Done

When grilling onions, it’s important not to overcook them. The last thing you want to do is burn the onions. So, look for a golden brown, translucent, or slightly charred around the edges to tell if they are done.

Also, inserting a fork into the center of the onion should be soft but not mushy.

What Do You Season Grilled Onions With?

Most people, myself included, will season the onions with olive oil, salt, and black pepper. That said, you can get as creative as you want with your seasoning.

Some other options include:

  • Garlic powder
  • Cumin
  • Paprika
  • Chili powder
  • Oregano
  • Thyme
  • Rosemary

If you’re looking for something a little sweeter, try using brown sugar, honey, or even balsamic vinegar.

The bottom line is to use whatever seasonings you like. Just be sure to season the onions before grilling, so the flavors have a chance to meld together.

Final Word

Now you know everything there is to know about grilling onions in foil. The only thing left is to go out, grill those onions, and enjoy them in whichever way you can think of. 

Make your own burgers, or add your onions to top off your steak or fajitas. Eat them whichever way you like. Bon Appetit!

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