Make the chicken: In a large skillet over medium-high heat, saute the chicken, onions, and garlic in oil until chicken is no longer pink. Transfer to a bowl and set aside.
In same skillet, whisk together orange juice, soy sauce, sugar, and ginger. Separately whisk vinegar and cornstarch. Bring orange mixture to a simmer over medium-high heat, then quickly whisk in cornstarch mixture until smooth. Stir sauce occasionally until thickened.
Add chicken back to skillet and toss to coat. Keep chicken warm.
Make the orzo: In a small saucepan, melt butter then saute garlic until fragrant. Remove from heat and stir in herbs. Pour butter mixture over hot orzo and toss to coat. Season orzo with salt and pepper to taste and serve warm with orange chicken. Enjoy!