Season chicken pieces with salt, pepper, and dried oregano.
Heat olive oil in a large deep skillet over medium-high heat.
Add chicken and sear until browned on all sides, approximately 5 to 7 minutes. Remove chicken from skillet and set aside.
Add diced onion to the same skillet and sauté for 3 minutes until translucent.
Stir in garlic and dry orzo, toasting the pasta for 2 minutes while stirring constantly.
Pour in chicken broth and heavy cream, scraping the bottom of the pan to deglaze.
Return chicken to the skillet, bring to a simmer, then reduce heat to low and cover.
Cook for 10 to 12 minutes until the orzo is tender and most of the liquid is absorbed.
Remove from heat and stir in baby spinach, parmesan cheese, and lemon juice until the spinach is wilted and the cheese is incorporated.
Serve immediately.