Whisk together Hellmann's® or Best Foods® Real Mayonnaise, soy sauce and garlic powder in small bowl. Remove 1/4 cup of mixture cover, and reserve, refrigerated.
Whisk orange juice into remaining mayonnaise mixture.
Pour 1/4 cup marinade over chicken in medium nonaluminum bowl or resealable plastic bag; turn to coat. Cover, or close bag, and marinate in refrigerator, turning occasionally, 3 to 8 hours. Refrigerate remaining marinade.
Remove chicken from marinade, discarding marinade. Grill chicken, turning occasionally and brushing frequently with 1/4 cup of the refrigerated marinade, 12 minutes or until thoroughly cooked.
Divide reserved Mayonnaise, soy sauce and garlic powder mixture between 4 buns. Grill buns until browned. Slice chicken and serve in buns.