Step 1: Season the chicken pieces with salt, pepper, and dried oregano. In a large skillet, heat olive oil over medium-high heat and sear the chicken until golden brown on all sides (about 5-7 minutes). Remove chicken from the pan and set aside.
Step 2: In the same skillet, melt the butter. Add the diced onion and sauté for 3 minutes until translucent. Stir in the minced garlic and cook for another 60 seconds until fragrant.
Step 3: Add the dry orzo to the skillet. Stir constantly for 2 minutes to toast the pasta until it becomes slightly golden and smells nutty.
Step 4: Pour in the chicken broth and lemon juice, using a wooden spoon to scrape up any browned bits from the bottom of the pan. Bring to a boil.
Step 5: Return the chicken to the skillet. Reduce heat to low, cover with a lid, and simmer for 10-12 minutes, or until the orzo is tender and most of the liquid has been absorbed.
Step 6: Remove the lid and stir in the baby spinach and Parmesan cheese. Continue stirring for 1-2 minutes until the spinach is wilted and the sauce is creamy. Serve immediately with extra lemon wedges if desired.