In a medium bowl, whisk the orange zest, orange juice, brown sugar, vinegar, soy sauce, chili sauce, ginger, and cornstarch together until combined. Set aside.

Drizzle oil into a large skillet that has been heated over medium to medium high heat. Add half of beef, breaking up any clumps and cook without stirring for one minute. Stir beef and continue to cook until browned, about 2 minutes. Transfer cooked beef to a bowl and cover.

Repeat with remaining beef and transfer to bowl.

Whisk prepared orange sauce and add to the same skillet the beef was cooked in. Cook sauce over medium heat until thickened, about 2-3 minutes.

Return cooked beef and any accumulated juices to skillet and toss to coat with the sauce.

Serve beef over cooked rice and garnish with sliced green onions. Serves 4.