Drain pineapple, reserving 2/3 cup juice. Combine cornstarch and soy sauce, stirring until cornstarch dissolves. Stir in reserved pineapple juice, brown sugar, and crushed red pepper.
Heat oil in a large nonstick skillet over medium-high heat. Add chicken and ginger; cook 3 minutes on each side or until chicken is browned. Add peppers and garlic; sauté 2 minutes.
Add cornstarch mixture; cook, stirring frequently, 3 minutes or until sauce thickens slightly. Add pineapple; cook 2 minutes. Serve over rice.