I Put Sliced Onions Under My Potatoes Before Roasting Them—Here’s Why

I usually toss potatoes and onions together before roasting, but this method changes where everything goes on the sheet pan. Thin slices of onion go down first, followed by potatoes placed cut-side down on top.

That small change gives the onions direct contact with the hot pan, where they brown and caramelize under the potatoes. At the same time, the potatoes develop crisp cut sides while picking up flavor from the onions and herbs underneath.

Best part is that the whole dish takes about 10 minutes to get into the oven.

Put the Herbs and Onions Down First

Start by heating the oven to 450°F and lining a rimmed baking sheet with foil.

Toss 2 pounds of halved small new potatoes with ¼ cup olive oil and 1 teaspoon salt. Sprinkle 2 tablespoons of chopped rosemary and thyme across the baking sheet, then spread one thinly sliced Vidalia onion over the herbs.

Potatoes go on last, with every cut side facing the pan. Pour any olive oil left in the bowl over the top.

Keeping the Onions Underneath Changes How They Roast

Onions mixed among potatoes don't always get enough contact with the pan to brown. Here, the thin slices sit underneath while the potatoes roast above them.

The onions soften, brown, and develop sweeter roasted edges as the potatoes cook. Rosemary and thyme are also trapped underneath, putting them in contact with the onion, oil, and heat rather than leaving all the herbs exposed on top.

Meanwhile, placing the potatoes cut-side down gives their flat surfaces a chance to brown against the hot sheet pan.

Roast Until the Potato Edges Turn Brown

Roast everything for 30 to 35 minutes, or until the potatoes are tender inside and browned around the edges.

Transfer the potatoes and onions to a bowl while they're still hot. Toss them with about ½ cup of chopped chives and tarragon, then finish with flaky sea salt to taste.

Adding these herbs after roasting keeps their flavor distinct from the rosemary and thyme that cooked underneath the potatoes.

Don't Microwave the Leftovers

Roasted potatoes lose much of their crisp texture once refrigerated, but the oven can bring it back.

Spread leftovers across a baking sheet and reheat them in the oven rather than using the microwave. Giving the potatoes space on the pan helps the exterior crisp again instead of steaming.

Next time you're roasting potatoes and onions together, don't mix everything before it hits the pan. Putting the onions underneath takes no extra prep, but changes what happens to both ingredients in the oven.

Do you roast onions underneath your potatoes, or have you always tossed the two together?