Preheat oven to 450°F.
Place potatoes in a large sauce pot, cover with water by at least 1 to 2 inches and place over high heat to bring up to a boil. Once boiling, add some salt and cook until potatoes are tender, about 10-12 minutes.
While potatoes are cooking, trim silver skin or connective tissue off tenderloins with a very sharp thin knife.
Place them on a non-stick cookie sheet with a rim. Coat tenderloins with EVOO then sprinkle with the grill seasoning. Transfer to oven and roast for 25-30 minutes, until the internal temperature reaches 145°F.
Place green beans and half the chopped onion onto a cookie sheet, drizzle with a little EVOO and season with some salt and pepper.