Preheat the oven to 375°F (190°C).
In a medium saucepan, bring the chicken broth to a boil. Add the rice, reduce heat to low, cover, and simmer for 15 minutes or until the rice is tender and liquid is absorbed. Remove from heat and let cool slightly.
While the rice cooks, heat olive oil in a skillet over medium heat. Add the chopped onion and cook for 3-4 minutes until translucent.
Add the minced garlic and diced red bell pepper to the skillet and cook for another 2-3 minutes until softened. Remove from heat.
In a large bowl, combine the cooked rice, sautéed vegetables, thawed peas, Parmesan cheese, Italian seasoning, salt, black pepper, and chopped parsley. Mix well.
Using a sharp knife, carefully cut a pocket into the side of each chicken breast, being careful not to cut all the way through.
Stuff each chicken breast pocket with the rice mixture, dividing it evenly among the four breasts.
Place the stuffed chicken breasts in a baking dish. Sprinkle shredded mozzarella cheese evenly over the top of each chicken breast.
Bake in the preheated oven for 30-35 minutes, or until the chicken is cooked through and the cheese is melted and golden.
Remove from the oven and let rest for 5 minutes before serving.