Heat olive oil in a skillet over medium heat. Add spinach and garlic and cook, stirring, until the spinach has wilted, 3 to 4 minutes.
Place chicken breasts in an ungreased 9x12-inch baking pan. Spread artichoke spinach mixture evenly over the chicken.
Bake in the preheated oven until the chicken juices run clear and the edges of the cheese topping are starting to brown, 25 to 30 minutes.
Set an oven rack about 6 inches from the heat source and preheat the oven's broiler.