Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
In a bowl, combine the cooked lentils, dry quinoa (preferably pre-rinsed and lightly toasted), egg, and rolled oats. Season with salt, pepper, and garlic powder. Using a fork or a potato masher, mash the mixture until it binds together but retains some texture.
Form the mixture into small, compact patties.
Heat a non-stick pan over medium heat and lightly spray with cooking spray or a tiny drizzle of olive oil. Sear the patties for about 3-4 minutes on each side until they become crispy and golden. Alternatively, for a lower oil option, place them on a lightly oiled baking sheet and bake for 15-20 minutes, flipping halfway.
Meanwhile, chop the zucchini and red bell pepper into bite-sized pieces. Toss them with a drizzle of olive oil, salt, and pepper, and spread them on a separate baking sheet.
Roast the vegetables in the oven for about 12-15 minutes until tender and slightly caramelized.
Plate the crispy lentil quinoa cakes and serve them alongside the roasted vegetables. Enjoy warm!