Roasted Poblano Smash Burgers on the Traeger

Smoky roasted poblanos, melty pepper jack cheese, sweet heat from candied jalapeños, and a spicy-tangy aioli take this In-N-Out–inspired 4×4 smash burger to the next level. Make roasted poblano smash burgers tonight!

Introduction: From In-N-Out to My Backyard Grill

There’s a lot to love about In-N-Out. The fresh ingredients, the consistent quality, the ability to build your burger exactly how you want it — whether that’s a humble single or a towering 4×4. For burger lovers, that flexibility is part of the magic. You’re not just ordering off a menu — you’re creating an experience, stacking flavors and textures to match your cravings in the moment.

I’ve always been fascinated by how they manage to make even the biggest stack still taste balanced. The meat-to-cheese ratio feels just right, the toppings never overpower, and the buns hold it all together like they were made for the job. That got me thinking: what if I took the 4×4 concept, brought it to my Colorado backyard, and gave it a Tex-Mex twist that makes every bite explode with flavor?

The answer: this Roasted Poblano Smash Burger. Instead of big, heavy patties, we go with thin, 2-ounce patties smashed directly into a pile of roasted poblano peppers. That means each layer has crispy edges, smoky depth, sweet heat from candied jalapeños, and a cheesy melt that ties it all together. And yes — a 4×4 here is perfect for sharing (though I won’t judge if you keep it all for yourself). The best part? Every element of this burger can be prepped and cooked right on the flat top, making cleanup easy and the flavor completely unmatched.

The Inspiration Behind This Burger

Growing up in Colorado, I didn’t have In-N-Out nearby until relatively recently. Now that they’ve moved into the area, I’ve had the chance to explore their menu and — of course — the not-so-secret menu. The 4×4 has always caught my eye: four patties, four slices of cheese, and a sense of indulgence that makes it a true treat. It’s bold, unapologetic, and the kind of order you only place when you’re ready to commit.

But I wanted more than just beef and cheese. I wanted layers of flavor — a burger that told a story as you ate it. That’s where poblanos come in. Mildly spicy, smoky when roasted, and versatile enough to pair with cheese, avocado, and jalapeños, they’re the perfect foundation for a burger that’s both over the top and totally manageable.

And here’s the bonus: because each patty is only 2 ounces, you don’t get the heaviness of a single thick burger. Instead, you get crisp edges, juicy centers, and that irresistible griddle-seared crust repeated four times in one burger. That’s what takes this from “good” to “let’s make this again next weekend.”

The Burger Smasher: Your Smash Burger Secret Weapon

What Makes the Burger Smasher a Must-Have Tool

The Burger Smasher (a heavy-duty, pre-seasoned cast-iron press) takes the guesswork out of achieving that perfect smash: it flattens a meatball into a consistently thin patty that blossoms into ultra-crispy edges while sealing in juiciness. One reviewer called it “a game changer… sears the meat to perfection, creating that delicious crispy edge while keeping the inside juicy.” The weighted, cool-touch handle lets you smash confidently and safely — plus cleanup is as simple as a quick wipe-down.

Alternative Uses Beyond Burgers

This tool isn’t just for smash burgers — it’s a real multitasker in the backyard kitchen. Here’s what else it excels at:

• Quesadillas & Grilled Sandwiches: Evenly presses ingredients together and creates a golden crust.
• Bacon, Paninis, and Tortillas: Maintains steady contact and ensures even crisping.
• Vegetables & Hash Browns: Keeps staples pressed flat for better browning and caramelization.

It’s a grill-side workhorse that’ll elevate your Traeger routine without clutter.

No Burger Smasher? Here’s What You Can Use Instead

Don’t have an official smasher on hand? No problem — here are a few tried-and-true substitutes:

Cast-Iron Press or Heavy Grill Weight

Tools like the Lodge Cast Iron Burger Press or a generic heavy grill press apply the same flat, even pressure, and they bring plenty of flavorful crunch too.

Wide Spatula or Flat Turner

A wide, thin-edge stainless steel spatula lets you press the beef down yourself. It may take two tools (one to press, one to flatten), but it still gets good crust, especially if you hold for a few seconds.

Heavy Plate or Sturdy Lid

In a pinch, a heavy lid or plate wrapped in foil works. It may not get the same thinness or edge-crispiness, but it gets the job done — especially if you give it a good stamp for 10–15 seconds. The key is even pressure and high heat.

Why a 4×4 Smash Burger Works Better Than One Big Patty

A half-pound burger patty is a lot — and it can be tricky to cook evenly without drying it out. By splitting that into four thin patties, you get more crust-to-meat ratio, which is where the flavor magic happens. That crust is the result of the Maillard reaction — when heat meets protein and sugar, transforming them into a deeply savory, slightly nutty, caramelized exterior. And the more surface area you have, the more of that flavor you can create.

On top of that, smashing the patties directly onto chopped roasted poblanos means every bite has charred pepper pieces integrated right into the meat. The poblanos caramelize, the beef crisps up, and the cheese melts into all the nooks and crannies. It’s a technique that locks in flavor rather than piling it on top as an afterthought.

Plus, because the patties cook so quickly, they stay juicy without overcooking. Layering cheese between each patty keeps the heat and moisture trapped inside while creating the ultimate melty, gooey bite from top to bottom.

Why Poblanos Are the Secret Weapon in This Burger

Poblanos aren’t a novelty ingredient in my kitchen — I use them year-round in everything from chili to stuffed pepper dishes. They’re mild enough for the kids to try (though this burger is more of a grown-up dinner in our house), but they bring so much complexity to the table that even a simple dish feels elevated.

When you roast poblanos, you unlock layers of flavor:

• Smokiness from charred skin
• Sweetness from caramelized sugars
• Mellow heat that lingers without overpowering
• Earthiness that plays perfectly with beef and cheese

For this burger, roasting the peppers first and then chopping them into small pieces gives you the perfect mix of crisped bits and tender bursts of flavor. They almost melt into the burger patty, while still offering enough texture to make each bite interesting.

How to Roast Poblanos for Smash Burgers

You can roast poblanos several ways — all of them work, but each gives a slightly different result.

On the Grill (Traeger or Gas)

Place whole poblanos directly over high heat. Turn every 30 seconds until the skins are blistered and blackened on all sides.

With a Blow Torch

This is my go-to for speed and drama. Hold the torch about 3–4 inches from the pepper and rotate until the skin is charred.

Under the Broiler

Place poblanos on a sheet pan and broil on high, flipping halfway, until blistered.

Pro Tip: Always steam roasted poblanos in a covered bowl or bag for about 10 minutes before peeling. This loosens the skin and makes them much easier to work with.

[Process Photo: Roasting poblano peppers on the griddle]
Alt text: Whole poblano peppers blistering on a hot Traeger Flatrock griddle.

Ingredients for the Roasted Poblano Smash Burger

• 8 oz 80/20 ground beef (divided into four 2oz balls)
• 4 whole poblano peppers, roasted, peeled, and chopped
• 4 slices pepper jack cheese
• 2 potato buns
• 1 avocado, smashed
• 2 tbsp mayo (1 tbsp for aioli + about 2 tsp for bun toasting)
• 1 tbsp spicy taco sauce or hot sauce (for aioli)
• 2–3 tbsp homemade candied jalapeños (or store-bought)
• Pickles (optional for extra tang)
• Tex-Mex seasoning blend

Tips for Perfect Roasted Poblano Smash Burgers Every Time

1. Start Hot – Your griddle or skillet should be preheated so the beef sears immediately.
2. Smash Once – Press down hard the first time and resist pressing again — you’ll squeeze out the juices.
3. Cheese Early – Add cheese right after flipping so it melts fully.
4. Toast the Buns with Mayo – Gives a perfect golden crust and extra flavor.
5. Serve Immediately – Smash burgers are best hot and fresh.

Step-by-Step: How to Make the Roasted Poblano 4×4

1. Roast the Poblanos

Grill, torch, or broil until skins are blistered and black. Steam in a covered bowl, peel, seed, and chop.

2. Prep the Beef & Season

Roll beef into 2-ounce balls and season lightly with Tex-Mex blend.

3. Smash the Patties

Place chopped poblanos on hot griddle, set beef ball on top, and smash firmly using your Burger Smasher tool. Cook 1–2 minutes until edges are crispy.

4. Flip & Add Cheese

Flip, top with pepper jack cheese, and let melt.

5. Prep the Buns

Spread mayo on cut sides, toast until golden brown.

6. Assemble the Burger

Spread avocado on bottom bun, add two patties, candied jalapeños, pickles, and aioli. Repeat with remaining patties.

Why the Traeger Flatrock is Perfect for Roasted Poblano Smash Burgers

The Traeger Flatrock offers even heat across the surface, so every patty gets a consistent crust. It’s also large enough to roast poblanos, smash patties, and toast buns all at once. That means less juggling and more time focusing on perfecting your burger.

Flavor Breakdown: Why This Burger Works

• Smoky heat from poblanos
• Creaminess from avocado and pepper jack
• Sweet heat from candied jalapeños
• Tang from aioli and pickles
• Crunch from golden-toasted buns

Every bite is layered and balanced — exactly what a 4×4 should be.

Variations to Try

• Swap poblanos for Anaheim peppers for a milder burger.
• Use Oaxaca cheese for a different melty texture.
• Add crispy bacon for extra indulgence.
• Make a “2×2” version for a smaller serving.

Alternate Recipes You’ll Love

• Honey Habanero Butter Burgers
• Green Chile Smash Burger Tacos
• Green Chile Smash Burgers
• Ultimate BBQ Cheeseburgers

What are you waiting for? Burgers can’t make themselves

This Roasted Poblano Smash Burger is my idea of a perfect backyard dinner — big flavor, crispy edges, smoky heat, and enough decadence to make any night feel special. If you’re an In-N-Out fan, you’ll love this 4×4 with a twist.

Fire up your grill, roast some poblanos, and give this burger a try. And if you make it, tag me — I want to see your version and hear how many layers you decided to stack.