Start by preheating your oven to 375°F (190°C). Lay the chicken breasts flat on your cutting board. Use a sharp knife to cut a deep pocket along the side of each piece—but don’t cut all the way through. You want to make space for the stuffing to stay inside.
Next, layer the inside of each chicken pocket with slices of roasted red pepper, fresh spinach leaves, and shredded mozzarella. I stuffed mine pretty generously—it’s what makes this dish ooze with flavor. If needed, secure the pocket with toothpicks so nothing escapes while baking.
In a small bowl, mix olive oil with garlic powder, Italian seasoning, salt, and pepper. Brush this flavorful blend over both sides of each chicken breast. Don’t skip this part—it makes the outside deliciously seasoned and golden when baked.
Place the stuffed chicken into a baking dish. Pop it in the oven and bake for 25 to 30 minutes. The chicken is done when it’s no longer pink in the center and juices run clear. Mine was done in 28 minutes, and the cheese was perfectly melty.