Combine first 7 ingredients in a medium bowl; toss to coat.
Heat oil in a large nonstick skillet or wok over medium-high heat until hot. Add steak and marinade to pan; cook 3 minutes or to desired degree of doneness. Add shrimp and bell peppers, and cook, stirring constantly, 3 minutes or just until shrimp turn pink. Serve immediately over hot cooked rice. Garnish, if desired.