BBQ Barramundi Burger with Grilled Cos

There is something magical about the way fire transforms food, and this burger came to life during an accidental backyard BBQ experiment. I had planned for a standard fish burger, but when the lettuce tumbled onto the grill and the lemons started sizzling, everything changed. That smoky sweetness from the cos and the way the grilled lemons deepened the tartare sauce made this an instant legend in my household.

Last summer my mate Dave, who claims to hate fish burgers, took one bite and went completely silent. When he finally looked up, he asked if I had been hiding culinary training. The best part is how the charred flavors just work together, making every bite feel like summer even in the middle of winter.

Ingredients

• 4 barramundi fillets (skinless): This fish is perfect for grilling because it holds together beautifully and has this naturally buttery taste that pairs so well with smoke
• 2 tbsp olive oil: Use something decent quality here because it really does make a difference to the final flavor
• Zest of 1 lemon: Fresh zest brings this bright aromatic quality that you just cannot get from bottled juice
• 1 garlic clove, minced: Do not use garlic powder here because fresh garlic creates this mellow sweetness when grilled
• 1 tsp sea salt: Flaky sea salt if you have it, but whatever you use, do not be shy with it
• ½ tsp freshly ground black pepper: Freshly cracked adds this little kick of heat that really wakes everything up
• 4 brioche or burger buns: Brioche gives you that slight sweetness that balances the tangy tartare perfectly
• 1 large head cos lettuce: Grilling this is the game changer that nobody expects but everyone loves
• 1 lemon, halved: Grilling the lemons caramelizes the natural sugars and makes the juice taste so much more complex
• 2 jalapeños: The grill tames the heat just enough while adding this smoky dimension that is incredible
• ½ cup good-quality mayonnaise: This is the base of your tartare, so use something you actually like eating
• 2 tbsp capers: These little briny bombs add these pops of salt and tang that cut through the rich fish
• 1 tbsp each of dill and parsley: Fresh herbs are non-negotiable here because they add brightness that dried herbs cannot match
• 1 small shallot: Shallots are milder than onions and add this subtle sweetness that really works
• 1 tsp Dijon mustard: Just enough to give the tartare some backbone without overwhelming everything else

Instructions

Preheat your BBQ or grill to medium-high heat:

You want it hot enough that you hear a satisfying sizzle when the fish hits the grates but not so aggressive that everything burns before it cooks through

Marinate the fish:

Whisk together the olive oil, lemon zest, garlic, salt, and pepper in a shallow dish, then add the barramundi fillets and let them hang out for about 10 minutes

Prep the cos lettuce:

Separate the lettuce into nice big leaves and brush them very lightly with olive oil so they do not dry out on the grill

Grill the lemons and jalapeños:

Place the lemon halves cut side down along with the jalapeños on the grill for 3 to 4 minutes until they are nicely charred and softened, then let them cool slightly before finely chopping the jalapeños and squeezing out all that beautiful grilled lemon juice

Make the tartare sauce:

Stir together the mayonnaise, chopped grilled jalapeños, 2 tablespoons of that grilled lemon juice, capers, both herbs, shallot, mustard, and some salt and pepper, then pop it in the fridge until you need it

Grill the barramundi:

Cook those marinated fillets for 3 to 4 minutes on each side until they are just cooked through with some lovely char marks

Grill the lettuce:

Throw the cos leaves on for just 1 to 2 minutes per side until they are slightly wilted and have picked up some smoky flavor

Toast the buns:

A quick toast on the grill keeps the bun from getting soggy and adds another layer of that irresistible grilled flavor

Build your masterpiece:

Spread that tartare sauce generously on both bun halves, then stack up with the grilled cos lettuce, a beautiful piece of barramundi, and fresh tomato and cucumber slices

Serve immediately:

Get these into hands while everything is still warm and the lettuce still has that perfect slight crunch

Pin It

This burger has officially become the thing my friends request most often, and I never get tired of watching their faces when they take that first bite. There is something about the combination of smoky, tangy, and fresh that just works on every level.

Grill Temperature Mastery

Getting the grill heat right is what makes or breaks this recipe. Too hot and the outside burns before the inside cooks, too cool and you miss out on those gorgeous char marks that add so much flavor. I have found medium-high is the sweet spot where everything caramelizes beautifully without turning to charcoal.

Fish Substitutions That Work

While barramundi is my go-to for its texture and taste, I have had great success with snapper, cod, and even mahi mahi when barramundi is not available. The key is choosing a firm white fish that will not fall apart on the grill. Ask your fishmonger what they recommend that day because sometimes the catch is surprisingly perfect for this recipe.

Make-Ahead Magic

The tartare sauce actually gets better after a day in the fridge, so I often double the batch and keep some for fish tacos, potato salad, or just straight-up on crackers. The grilled lemon flavor develops and intensifies beautifully overnight.

• Grill extra lemon halves while the grill is hot and freeze the juice for future batches
• The fish marinade works beautifully on chicken or even grilled vegetables
• Leftover tartare sauce keeps for up to a week in the fridge, if it lasts that long

Pin It

Grab some napkins and maybe eat this outside because things might get gloriously messy. Every bite will remind you why grilling season is the best time of year.

Recipe FAQs

→ What is barramundi and can I substitute it?

Barramundi is a mild, buttery Australian white fish with a flaky texture that holds up beautifully on the grill. If unavailable, substitute with snapper, cod, sea bass, mahi-mahi, or any firm white fish fillet. Adjust cooking time slightly depending on fillet thickness.

→ How spicy is the grilled lemon jalapeño tartare?

The tartare offers mild to medium heat, depending on the jalapeños. Removing the seeds and membranes tames the spice significantly while still delivering that signature jalapeño flavor. For extra kick, leave some seeds in or add a dash of hot sauce. The grilled mellowing process creates a smoky heat rather than sharp burn.

→ Why grill the lettuce and lemon?

Grilling cos lettuce transforms it—wilting the leaves slightly while adding subtle smokiness that complements the fish beautifully. Grilling lemons concentrates their natural acidity and caramelizes the sugars, creating a complex citrus brightness that fresh lemons can't match. Both techniques elevate the burger from ordinary to extraordinary.

→ Can I cook these indoors?

Absolutely. Use a grill pan or heavy skillet over medium-high heat to achieve similar char marks and flavor. You can also use the broiler for the lemons and jalapeños, though they won't develop quite the same smoky depth. A cast-iron pan works exceptionally well for the barramundi fillets.

→ How do I prevent the barramundi from sticking to the grill?

Ensure your grill grates are clean and well-oiled before heating. Pat the barramundi fillets dry, then coat them thoroughly in the olive oil marinade. Let the grill reach proper medium-high temperature—placing fish on a lukewarm grate guarantees sticking. Wait until the fish releases naturally before flipping, usually after 3-4 minutes.

→ What sides pair well with these burgers?

Crisp, refreshing sides balance the rich fish and tangy tartare. Try a simple green salad with vinaigrette, roasted potato wedges with sea salt, or grilled corn on the cob. For true Australian flair, serve with a crisp Sauvignon Blanc or a cold pale ale as suggested in the original pairing notes.