In a medium saucepan, bring the vegetable broth to a boil over medium heat. Add the orzo and cook according to package instructions, usually about 8-10 minutes, until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the chopped red onion and minced garlic, sautéing for about 2-3 minutes until the onion becomes translucent.
Add the diced zucchini and bell pepper to the skillet. Sauté for another 5 minutes until the vegetables are tender.
Stir in the halved cherry tomatoes and spinach, cooking for an additional 2-3 minutes until the spinach wilts.
Add the cooked orzo to the skillet along with the lemon juice and zest. Toss everything together until well combined. Season with salt and pepper to taste.
Remove from heat and let it sit for a minute to allow the flavors to meld together.
Serve warm, garnished with fresh basil leaves and, if desired, crumbled feta cheese on top.