Preheat your oven to 350°F (175°C).
In a large skillet, heat olive oil over medium heat. Add the diced bell pepper, onion, and celery. Sauté for about 5 minutes, until the vegetables are tender.
Add the peeled shrimp to the skillet and cook for another 3-4 minutes until the shrimp are pink and opaque.
In a mixing bowl, combine the cream of mushroom soup, milk, garlic powder, paprika, salt, and pepper. Mix well until fully combined.
In the skillet with the shrimp and vegetables, add the cooked rice and then pour the soup mixture over the top. Stir until the ingredients are well combined.
Transfer the shrimp mixture into a greased 9x13 inch baking dish.
Sprinkle the shredded cheddar cheese evenly over the top of the casserole. Follow with an even layer of breadcrumbs.
Place the baking dish in the preheated oven and bake for about 30 minutes, or until the top is golden brown and bubbly.
Remove from the oven and let it cool for a few minutes. Garnish with fresh parsley if desired before serving.