Whisk together oil, orange juice, rosemary and garlic in a mixing bowl. Pour 1/4 cup of the marinade into a small bowl and set aside. Add olives to the mixing bowl and stir to combine.
Cut chicken thighs into quarters, season with salt and pepper to taste then combine with olive vinaigrette. Turn to coat and allow to marinate for about 15 minutes.
Heat a large skillet over high heat. Add chicken and olive mixture spreading into an even layer. Cook chicken for 3 to 4 minutes per side or until chicken is completely cooked, well browned and sauce is reduced and thickened. Remove from heat, transfer chicken and sauce to a serving plate and set aside.
Return skillet to medium heat; add reserved 1/4 cup vinaigrette, onions, salt and pepper. Cook for 1 to 2 minutes or just until onions begin to soften. Add kale and cook 1 to 2 minutes more or just until kale begins to turn bright green and soften. Serve immediately with chicken.