Preheat grill to medium-high heat. Season chicken breasts with salt and pepper.

Grill chicken for about 3-4 minutes per side, or until cooked through and no longer pink in the center. Remove from grill and set aside.

While chicken is grilling, heat olive oil in a skillet over medium heat. Add minced garlic and sauté for 30 seconds until fragrant.

Add the thawed and squeezed dry spinach to the skillet. Cook, stirring, for 2-3 minutes until heated through. Season with a pinch of salt and pepper if desired.

Place the grilled chicken on a baking sheet. Divide the spinach mixture evenly over each chicken breast. Top with shredded mozzarella cheese and sliced roasted red peppers.

Broil for 1-2 minutes, or until the cheese is melted and bubbly. Serve immediately.