This grilled portobello and roasted red pepper sandwich makes a solid lunch when you want something filling but still fresh. Featured in Go Vegan, Marlene Watson-Tara shares this simple, whole-food sandwich as part of her everyday approach to vegan cooking. Juicy grilled mushrooms, roasted peppers, and crisp greens give it plenty of texture. It works well for a quick lunch or to pack for later.
The portobello mushrooms soak up a marinade of balsamic vinegar, shoyu, garlic, and ginger. Once grilled, they turn tender and rich, with a deep savory flavor. Roasted red peppers mixed with oil-free mayonnaise add creaminess and a slight sweetness. Fresh tomatoes and salad leaves keep the sandwich bright and balanced.
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Serve the sandwiches warm in toasted sourdough baguettes. They work well on their own or with a simple salad or fries. Leftover mushrooms keep in the fridge and can be reheated or sliced cold into salads the next day.
Portobello and roasted red pepper sandwich method

Ingredients
- 2 tbsp balsamic vinegar
- 2 tbsp shoyu
- 3 garlic cloves minced
- 1 tbsp freshly squeezed ginger juice
- 1 tbsp water
- 4 Portobello mushroom caps
- 1 cup roasted red pepper chopped
- 4 tbsp. oil-free mayonnaise
- 4 sourdough baguettes toasted
- 4 tomatoes thinly sliced
- Fresh salad greens rocket, arugula etc.,
Instructions
- Mix the first five ingredients in a measuring jug.
- Clean the mushrooms, remove the stems and place the mushroom caps in a container.
- Pour over the marinade, seal with a lid and set aside for at least two hours to allow to marinate.
- In a small bowl, mix the red pepper with the mayonnaise and set aside.
- Preheat the grill to medium. Place mushrooms, gill sides down, on a parchment-lined baking sheet. Grill for 4 minutes on each side.
- Place the buns, cut sides down, on the grill rack and toast each side. Spread the mayonnaise mixture on the base of each bun.
- Top with the mushroom, tomato and salad greens.
- Add some relish of your choice if desired.
Republished with permission from Go Vegan: A Guide to Delicious, Everyday Food – for the Health of Your Family and the Planet by Marlene Watson-Tara, published by Lotus Publishing, 2019.
Marlene Watson-Tara is a plant-based nutrition educator, author, and co-founder of the Human Ecology Project. Her forthcoming book, Macrobiome: How the Planet Governs Human Ecology and a Healthy Microbiome, is scheduled to launch at the Oxford Literary Festival in March 2026. See their upcoming lecture at Oxford here, and learn more on their website MACROVegan.
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