Rinse the quinoa under cold water, then combine it with two cups of water or vegetable broth in a medium saucepan. Bring to a boil over medium-high heat.

Once boiling, reduce heat to low, cover, and let simmer for about 15 minutes. Remove from heat and let sit for 5 minutes, then fluff with a fork.

While the quinoa is cooking, prepare the vegetables by halving the cherry tomatoes, dicing the cucumber and bell pepper, and slicing the avocado.

In a large bowl, combine the spinach or mixed greens with the chopped vegetables.

Add the cooked quinoa to the bowl with the vegetables. Drizzle with olive oil and lemon juice, and season with salt and pepper. Toss gently to combine.

Sprinkle crumbled feta cheese on top and garnish with fresh herbs before serving.