In a large pot, sauce pan or cast iron dish, bring the chicken stock to a boil, add the orzo and cook for about 8 minutes, stirring occasionally. Set aside. The orzo will absorb all the stock.
Using a medium to large sized skillet over medium-high heat, heat the olive oil and sauté the garlic, onion, carrots, bell pepper, and celery for about 3-4 minutes. Season with salt and pepper.
Add in the olives and tuna and cook for an additional 2-3 minutes. Mix well. Lastly, mix in the cooked orzo and fresh parsley, toss together, let cook for a minute and serve.