Cook rice in 2 cups water as directed on package, omitting margarine and salt.
Meanwhile, heat oil in large nonstick skillet or wok over high heat until hot. Add beef and onion; cook 3 to 5 minutes or until beef is lightly browned, stirring occasionally.
Stir in broccoli, stir-fry sauce and 1/4 cup water. Reduce heat to medium; cover and cook 4 minutes or until broccoli is crisp-tender, stirring occasionally.
In measuring cup or small bowl, combine 2 teaspoons water and cornstarch; blend well. Add to skillet; cook and stir about 1 minute or until thickened. Serve over rice.