Step 1: Prepare the Red Onion 🧅

Peel 1 large red onion.

Slice it very thinly into rings or half-moons.

Try to keep the slices relatively consistent so they pickle at approximately the same rate.

Separate the onion layers gently with your fingers.

Step 2: Pack the Jar

Transfer the sliced onion to a clean pint-size jar.

Pack the onions loosely rather than forcing them down tightly.

Leaving some space between the layers allows the hot brine and spices to move throughout the jar.

How Thin Should You Slice Pickled Onions?

Thin slices work best for quick refrigerator pickles.

The thinner the onion, the more quickly the vinegar brine can penetrate it.

A sharp chef’s knife works perfectly well.

A mandoline can create extremely consistent slices, but use the appropriate hand guard and follow the manufacturer’s safety instructions.

Slightly thicker slices will remain crunchier but generally need more time in the refrigerator before the flavor fully develops.

Step 3: Add the Garlic

Thinly slice 3 garlic cloves.

Add them to the jar, distributing the pieces throughout the onion rather than leaving all of the garlic on top.

Step 4: Add the Spices 🌶️

Add:

• 1 teaspoon whole black peppercorns
• 1/2 teaspoon red pepper flakes
• 1/2 teaspoon mustard seeds
• 1/4 teaspoon dried oregano
• 1 small bay leaf

Distribute the seasonings throughout the jar as much as practical.

They’ll continue moving around once the hot brine is added.

Step 5: Make the Pickling Brine

Add the following to a small saucepan:

• 1 cup white vinegar
• 1/2 cup water
• 1 tablespoon kosher salt
• 1 tablespoon granulated sugar

Place the saucepan over medium heat.

Stir until the salt and sugar completely dissolve.

Bring the mixture to a gentle simmer.

There’s no need to aggressively boil the brine for an extended period.

Step 6: Pour the Hot Brine Over the Onions

Place the jar on a heat-resistant surface.

Carefully pour the hot brine over the onions and spices.

Pour slowly to reduce splashing.

The onions should be mostly submerged.

If necessary, gently press them beneath the brine using a clean spoon.

Why Use Hot Brine?

Hot brine helps dissolve the salt and sugar while beginning to soften the raw onion.

The heat also helps the aromatics begin releasing their flavors into the liquid.

However, these onions are still intended to retain some crunch.

You’re not trying to cook the onion until completely soft.

Step 7: Let the Jar Cool

Leave the jar uncovered until it cools to approximately room temperature.

This should take around 20–30 minutes.

Step 8: Refrigerate 🧊

Once cooled, seal the jar tightly.

Transfer it to the refrigerator.

Allow the onions to pickle for at least 1 hour before serving.

They’ll already have noticeable vinegar and spice flavor at this point.

For deeper flavor, refrigerate them for 12–24 hours.

What Happens as the Onions Pickle?

The transformation begins almost immediately.

The hot acidic brine starts softening the onion’s sharp raw bite.

Over time, the onion slices become more flexible while still retaining crunch.

Their purple pigment also begins moving into the brine, creating the gorgeous pink-purple color associated with pickled red onions.

Meanwhile, the garlic, peppercorns, chile flakes, mustard seeds, oregano, and bay leaf slowly season the liquid.

That’s why a jar that’s good after one hour is often even better the following day.

When Are Pickled Red Onions Ready?

You can begin serving them after approximately 1 hour of refrigeration.

At this stage they’ll remain quite crisp with a noticeable raw-onion character.

After 12–24 hours, they’ll generally have:

• A more pronounced vinegar flavor
• More developed garlic notes
• Better-distributed pepper flavor
• A slightly softer texture
• Deeper pink color

For the best balance of texture and flavor, making them the day before you need them works especially well.