Heat olive oil and garlic in a large skillet over medium-high heat. Sauté garlic for several minutes until golden brown. Remove garlic with a slotted spatula and discard.
Add chicken to hot skillet and cook until golden brown on each side, approximately 3-4 minutes per side. Season with salt and black pepper, to taste. Remove chicken from skillet and set aside.
Add half & half and chicken broth and scrape up any brown bits from the bottom of the pan with a spatula.
Add oregano and grated cheese to skillet and whisk until cheese is completely melted, approximately 3-4 minutes.
Reduce heat to just below medium and add the sun-dried tomatoes and baby spinach. Simmer until tomatoes are softened and the spinach wilts, stirring occassionally.
Add chicken and its juices back to skillet and simmer until chicken is heated through, 2-3 minutes. Taste and adjust seasonings, as desired.