Dressing: In a screw-top jar combine 2 tablespoons orange juice, the oil, and splenda; cover and shake well. Chill dressing until serving time.
For marinade, combine soy sauce, green onions, 2 tablespoons orange juice, the lemon juice, and garlic. Place chicken in a plastic bag set into a shallow dish. Add marinade; seal bag. Turn chicken to coat well. Chill 2 to 4 hours, turning chicken occasionally. Remove chicken from bag, reserving marinade. Grill chicken on an uncovered grill over medium coals for 5 minutes. Brush with marinade; turn chicken and brush with marinade. Grill 7 to 10 minutes more or until chicken is tender and no longer pink. Cool slightly; slice chicken breast. Discard any remaining marinade.
Line 4 individual plates with spinach leaves. Arrange strawberries, oranges, and chicken breast slices on spinach-lined plates. Shake dressing; drizzle over salads.