Heat gas or charcoal grill. In small bowl, mix onion powder, 2 teaspoons thyme, the garlic salt and pepper. Sprinkle thyme mixture on all sides of tenderloins. Immediately place on grill over medium heat. Cover grill; cook 15 to 20 minutes, turning 3 times, until meat thermometer inserted in center reads 160°F.
Meanwhile, in 12-inch skillet, heat oil over medium-high heat until hot. Cook remaining ingredients in oil 4 to 7 minutes, stirring frequently, until vegetables are tender.
To serve, cut tenderloins into slices. Spoon vegetable mixture over slices.