Serve these flavorful patties, packed with green lentils, brown rice, oats, veggies and seasonings, on top of a salad or cooked greens. The green lentils and brown rice can be cooked a day or two ahead of time, to help these burgers come together more quickly.
Put bell peppers, carrots, onions, oats and walnuts in a food processor. Pulse until all ingredients have been finely and evenly chopped. Transfer mixture to a large bowl. Add all remaining ingredients except olive oil. Stir to mix well.
Heat a tablespoon of olive oil in a cast iron or nonstick skillet over medium heat. Using a 1/4-cup measure, scoop mixture into balls, then flatten to form patties. If mixture seems crumbly and patties aren’t holding together, add a teaspoon or two of water, then remix and re-shape patties. Working in batches, cook patties on each side until browned, 2 to 3 minutes, flipping carefully. Serve warm.