Cook orzo according to package instructions; drain and transfer to a bowl.
Add 2 tablespoons oil and the parsley. Season with salt and pepper.
In a medium bowl, whisk garlic, 1 tablespoon oil, the brine, and 1/2 teaspoon pepper; toss with chicken.
In a large nonstick skillet heat remaining tablespoon oil over medium-high. Cook chicken until golden and cooked through, 5 to 8 minutes, flipping halfway through.
Transfer to a plate. Add tomatoes and their liquid, olives, and capers to skillet; boil until thickened, 4 minutes.
Stir in any juices from chicken and season with salt and pepper. Serve chicken with orzo and sauce.