Heat gas grill to medium-high or prepare charcoal grill with medium-hot coals.
Combine satay sauce, 2 tablespoons lime juice and 1/4 teaspoon each salt and pepper.
Thread tenders onto skewers; brush each with satay sauce. Grill skewers for 5 minutes per side or until chicken is cooked through. Grill scallions for last 3 minutes of cook time.
Meanwhile, stir together remaining 2 tablespoons lime juice, 1/4 teaspoon each salt and pepper, mangoes, red onion and vegetable oil in a bowl.
Remove chicken and scallions from grill and thinly slice scallions. Stir half of scallions into mango relish and sprinkle remaining half over meat. Serve skewers with relish.