Rinse the quinoa thoroughly under cold water using a fine-mesh sieve. This removes any bitter-tasting saponins.
In a medium saucepan, combine the rinsed quinoa with 2 cups of water or vegetable broth. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes, or until all the liquid is absorbed and the quinoa is cooked through.
While the quinoa is cooking, prepare the vegetables. Dice the cucumber, tomatoes, red onion, and bell pepper into small, bite-sized pieces. Chop the fresh parsley and mint.
In a large bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano, salt, and black pepper to create the lemon vinaigrette.
Once the quinoa is cooked, fluff it with a fork and let it cool slightly. Add the cooked quinoa to the bowl with the lemon vinaigrette.
Add the diced cucumber, tomatoes, red onion, bell pepper, chopped parsley, and mint to the bowl with the quinoa and vinaigrette. Gently toss everything together until well combined.
Taste the salad and adjust the seasoning as needed. You may want to add more lemon juice for extra tanginess or more salt and pepper to taste. Serve immediately or chill in the refrigerator for later. Garnish with crumbled feta cheese, if desired, before serving.
