Heat 1 tablespoon olive oil in a large nonstick skillet over medium heat.
Add 1 teaspoon dried oregano, 1 dash garlic powder, 1/2 teaspoon grated lemon peel, and 1/2 teaspoon black pepper; cook and stir just until fragrant, about 30 seconds.
Add the cubed chicken and cook, stirring, about 4 minutes until the outside is no longer pink.
Stir in 8 oz chicken broth, 1 1/4 cups uncooked orzo, 6 oz drained Greek olives, and 4 minced garlic cloves; bring to a boil over high heat.
Reduce heat to medium-low, partially cover, and simmer for 15 minutes, stirring occasionally, until the orzo is tender and the chicken is cooked through.
Remove from heat and stir in 2 cups baby spinach and 1/2 cup crumbled feta until the spinach wilts, about 2–3 minutes.
Serve immediately, topping with additional feta if desired.