Preheat oven to 375 degrees F and line a large baking sheet with aluminum foil.
Trim and quarter the Brussels sprouts and arrange on the baking sheet with the grapes, toss with olive oil, shallots, garlic, salt, and pepper. Spread evenly and roast until sprouts are tender and golden brown, about 20 minutes.
Remove from oven and stir in the chopped parsley and walnuts.
While the sprouts are roasting, season the chicken tenders liberally with salt and pepper. Place a medium pan over medium-high heat and add olive oil.
Add the chicken to the pan and cook until browned on the bottom, turn, and continue to cook until chicken is cooked through, about 3 to 4 minutes per side.
Place cooked chicken on a platter and spoon the sprouts over it.