In a large, oven-proof skillet (such as a cast iron), heat the olive oil over medium-high heat.
Add the onion and chicken sausage, and cook until the onion has softened, about 5-7 minutes.
Add the garlic, salt, pepper, and Italian seasoning, and cook for another minute.
Add the diced tomatoes, chicken broth, and quinoa. Stir to combine.
Bring the mixture to a simmer, reduce the heat to medium-low, and cover.
Simmer for 15-20 minutes, stirring occasionally, until the quinoa is fluffy and the chicken broth has been absorbed.
Stir in the chopped spinach and cook a few minutes until it's wilted.
Top with Italian cheese.
Turn on broiler.
Place pan in oven and broil until cheese has melted and is slightly golden.
Serve topped with chopped parsley. Enjoy!