Cook the orzo according to package instructions. Drain and set aside.
In a large skillet, heat olive oil over medium heat. Add the diced onion and sauté until translucent, about 3-4 minutes.
Add the minced garlic and cook for an additional minute until fragrant.
Increase the heat to medium-high and add the chicken pieces. Season with salt, pepper, and oregano. Cook until the chicken is browned and cooked through, about 5-7 minutes.
Add the bell pepper, zucchini, and cherry tomatoes to the skillet. Stir-fry for about 4-5 minutes until the vegetables are tender but still crisp.
Stir in the cooked orzo, spinach, lemon juice, and lemon zest. Mix well and cook for another 2-3 minutes until everything is heated through.
Taste and adjust seasoning if necessary. Serve hot, garnished with fresh parsley if desired.