Stir the broth, cornstarch, soy sauce and garlic powder in a medium bowl until the mixture is smooth.
Cook the beef in a 10-inch nonstick skillet over medium-high heat until it's well browned, stirring often. Add the pepper to the skillet and cook until it's tender-crisp, stirring often.
Reduce the heat to medium. Add the broth mixture to the skillet. Cook and stir until the mixture boils and thickens, stirring constantly. Serve over the rice.