In a medium saucepan, combine 1/2 cup of rinsed quinoa and 1 1/4 cups of water. Bring to a boil, then reduce the heat to low, cover, and simmer for about 15 minutes or until the quinoa is fluffy and the water is absorbed. Once done, remove from heat and let it cool slightly.
While the quinoa is cooking, heat 1 tablespoon of olive oil in a skillet over medium heat. Add the finely chopped onion and sauté for 3-4 minutes until soft. Add the zucchini and red bell pepper strips, cooking for another 5-7 minutes until the veggies are tender. Season with 1/4 teaspoon of sea salt and black pepper. Remove from heat and let cool.
In a large mixing bowl, combine the cooked quinoa, chickpeas, sautéed vegetables, egg, bread crumbs, grated Parmesan, parsley, oregano, and the remaining 1/2 teaspoon of sea salt. Mix well until all ingredients are evenly incorporated.
Using your hands, form the mixture into small patties, about the size of a slider. You should be able to create around 10 patties. If the mixture feels too wet, add a little more bread crumbs.
Preheat your oven to 375°F (190°C). Place the formed sliders on a baking sheet lined with parchment paper. Brush the tops with 1 tablespoon of olive oil for an extra crispy finish. Bake for 20-25 minutes, flipping halfway through, until golden brown.
Once the sliders are cooked, slice the whole-grain slider buns in half. Place a slider on the bottom half, add a lettuce leaf, and drizzle with balsamic vinegar for a zesty touch. Top with the other half of the bun and serve immediately.