Crispy Baked Fish Sandwiches with Avocado Mayo and Pickled Onion

Craving fried fish, but looking for something slightly healthier? Try these crispy baked fish sandwiches with avocado mayo and pickled onion. It’s the creamy, crunchy, tangy bite you’ve been looking for.

Crispy Oven Baked Fish Sandwiches with Mayo and Tangy Pickled Onions
Sally Vargas

If you ask me, a good fish sandwich has to hit all the right notes for texture and flavor in order to reign supreme. The fish needs to be tender, a creamy spread is essential, a hit of heat or tang is always good, and a soft bun is a must.

This crispy fish sandwich hits all of those notes and does the job right. It features a brioche bun slathered with avocado mayo, crispy baked fish, a double hit of flavor from the pickled onion and jalapeños and has a generous pile of shredded lettuce for extra crunch.

The bonus? Because the fish is baked and not fried, it’s a little healthier, too.

What Type of Fish to Use

A firm, sturdy white fish that’s not too thin works best here. If you can get a fillet of halibut, that’s a terrific choice. Cod and grouper will also work well for this recipe. Ask your local fishmonger for suggestions if you can’t find any of the fish listed.

Fish Sandwiches with Avocado Mayo
Sally Vargas

A Healthier Fish Sandwich

One of the recommendations from the US Dietary Guidelines (we summarized them for you here) is to incorporate more fish into our diets. A plate of deep fried fish, however, shouldn’t be your go-to option. This oven-baked version is a healthier spin on fried fish with plenty of pleasing crunch.

The crispy exterior is provided by the combination of panko breadcrumbs, a hot oven, and non-stick cooking spray. The other element that gives this sandwich a healthier edge is the avocado mayo so you’re getting more heart-healthy fats, not to mention fiber and other nutrients.

Swaps and Substitutions

Feel free to tinker with the sandwich ingredients to make them your own. Here are a few suggestions:

  • If you’re not keen on avocado: Use tartar sauce, plain mayo or a squeeze of sriracha for a spicy kick.
  • For a gluten-free sandwich, look for gluten-free panko at the market and use gluten-free sandwich buns.
  • For a lighter bite, skip the bun and enjoy the fish with all the fixings with a knife and fork or tucked into a crunchy lettuce wrap.
  • Skip the pickled jalapenos if you don’t like things spicy.

What to Serve with Crispy Fish Sandwiches

These sandwiches are pretty darn filling and packed with flavor, so you don’t need much for a side dish. A simple green salad will do or this Easy Cucumber Salad. In the summer, sliced tomatoes drizzled with olive oil and balsamic would be a good addition (and I’d never say no to steamed and buttered corn).

Crispy Oven Baked Fish Sandwiches with Mayo and Tangy Pickled Onions
Sally Vargas

Prefect for a Crowd

This is a perfect recipe to scale up and serve for a bigger group, say for game day or a birthday gathering. You could even make miniature fish sandwiches, by cutting the fish into eight pieces and serving them on slider buns.

You may need more panko, since the surface area of the fish will increase slightly. You’ll also want to cut the cooking time a bit, since the pieces of fish will be smaller.

Make Ahead Options

There’s plenty you can do several hours ahead of time with this recipe. Have it all prepped ahead of time then all you need to do is bake and assemble.

  • Bread the fish and refrigerate uncovered on a plate or rack. Wait to coat the baking sheet and fish with cooking spray right before it goes in the oven.
  • Make the pickled onions 
  • Make the avocado mayo. Cover the surface with plastic wrap and keep in the fridge until ready to use.
  • Shred the lettuce and refrigerate in a plastic bag or covered container.
Crispy Oven Baked Fish Sandwiches
Sally Vargas

More Crunch-tastic Sandwich Recipes

Crispy Baked Fish Sandwiches with Avocado Mayo and Pickled Onion

Prep Time 30 mins
Cook Time 12 mins
Total Time 42 mins
Servings 4 servings


For the pickled onion

  • 1/3 cup apple cider vinegar

  • 1 tablespoon sugar

  • 1 teaspoon kosher salt

  • 1/2 medium red onion, thinly sliced

For the fish sandwiches

  • 1 1/4 pounds firm white fish such as halibut, cod, or grouper

  • 1 1/4 teaspoons kosher salt, divided

  • 1/4 teaspoon ground black pepper

  • 1 cup panko style breadcrumbs

  • 1 tablespoon garlic powder

  • 1 tablespoon ground cumin

  • 2 large eggs

  • 1/4 cup all-purpose flour

  • Non-stick cooking spray

For the avocado mayo

  • 1 large ripe avocado, peeled and pitted

  • 1 tablespoon lime juice

  • 2 tablespoons mayonnaise

To serve

  • 4 soft sandwich buns, such as brioche

  • 2 cups romaine hearts, shredded

  • 2-3 tablespoons pickled jalapenos


  1. Preheat the oven, pickle the onions:

    Preheat the oven to 425° F.

    In a small shallow bowl, combine the vinegar, sugar, and 1 teaspoon salt and stir until the sugar and salt dissolve.

    Submerge the onions in the liquid and set aside. Stir the onions occasionally, pressing them into the liquid, while you prep the sandwiches.

    Red onions pickling in a glass bowl to make Crispy Oven Baked Fish Sandwiches.
    Sally Vargas
  2. Cut and season the fish:

    Cut the fish into 4 equal pieces that will work well with the bun size. Season all sides with 1 teaspoon kosher salt and black pepper.

    Raw fish fillets seasoned to make Crispy Oven Baked Fish Sandwiches.
    Sally Vargas
  3. Set up your workstations for the fish:

    Generously coat a baking sheet (the darker the better) with cooking spray.

    In a small shallow bowl, combine the panko, garlic powder, and cumin. In another small shallow bowl, crack and whisk the eggs. In a third shallow small bowl, add the flour.

    Organize your workstation as such: flour, eggs, panko, baking sheet.

  4. Dredge fish:

    Dip a piece of fish in the flour to coat it on all sides, shaking off excess. Submerge the fish in the beaten eggs, coating all sides, and allow the excess to drip off. Finally, dredge fish in the seasoned panko until thoroughly coated on all sides. Lay on the sheet pan. Repeat with the remaining pieces of fish.

    Fish fillets coated with flour to make Fish Sandwiches with Avocado Mayo.
    Sally Vargas
    Fish fillet dipped in egg to make Fish Sandwiches with Avocado Mayo.
    Sally Vargas
    Fish fillet coated in breadcrumbs to make Crispy Oven Baked Fish Sandwiches with Mayo and Tangy Pickled Onions.
    Sally Vargas
    Fish fillets on a baking sheet to make Crispy Oven Baked Fish Sandwiches with Mayo and Tangy Pickled Onions.
    Sally Vargas
  5. Coat fish with cooking spray and season:

    Generously coat the top of the fish with non-stick cooking spray as if adding a coat of paint. Sprinkle with a pinch of kosher salt over the top of each piece of fish.

    Spraying fish fillets with cooking oil for Crispy Oven Baked Fish Sandwiches with Mayo and Tangy Pickled Onions.
    Sally Vargas
  6. Bake fish:

    Bake the fish on the top rack of the oven, until nicely browned on the underside, and just cooked through (it should flake when you pry it in the center with a fork), 10 to 12 minutes depending on thickness of the fish.

    Baked fish fillets for Fish Sandwiches with Avocado Mayo.
    Sally Vargas
  7. Make avocado mayo:

    While the fish bakes, mash avocado in a small bowl using a fork. Add the lime juice, mayonnaise, and remaining 1/4 teaspoon kosher salt and combine until fairly smooth.

    Avacado mayo in a bowl to make Fish Sandwiches with Avocado Mayo.
    Sally Vargas
  8. Warm buns in oven:

    Place the buns on a baking sheet and put them in the oven to warm, about 1 minute. You want the buns soft and warm, not fully toasted.

  9. Assemble fish sandwiches:

    To assemble, spread avocado mayo on the bottom and top of the buns, top with the lettuce and followed by a piece of fish. Top the fish with a tangle of pickled onions and as many pickled jalapenos as you desire. Cover with the top bun. Serve.

Nutrition Facts (per serving)
788 Calories
32g Fat
76g Carbs
50g Protein
Show Full Nutrition Label Hide Full Nutrition Label
Nutrition Facts
Servings: 4
Amount per serving
Calories 788
% Daily Value*
Total Fat 32g 41%
Saturated Fat 7g 35%
Cholesterol 208mg 69%
Sodium 1516mg 66%
Total Carbohydrate 76g 28%
Dietary Fiber 12g 45%
Total Sugars 12g
Protein 50g
Vitamin C 18mg 88%
Calcium 234mg 18%
Iron 7mg 41%
Potassium 1797mg 38%
*The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.
Nutrition information is calculated using an ingredient database and should be considered an estimate. In cases where multiple ingredient alternatives are given, the first listed is calculated for nutrition. Garnishes and optional ingredients are not included.