Cut chicken breast into 1 inch pieces and set aside. In a large bowl, mix together olive oil, dijon, garlic, oregano, sumac, kosher salt, and pepper. Add in chicken breast and mix with the marinade till evenly coated. Cover and marinate for at least 30 minutes and up to 12 hours.
Cover a baking sheet with aluminum foil for easy clean up. Preheat oven to 425 degrees F. Thread alternating pieces of chicken, peppers, and shallots onto metal skewers. Bake for 15-20 minutes until cooked through, meaning no pink in the center and registering 165 degrees F on a meat thermometer.
If you'd like more of a grill-like char on the outside, set your oven broiler to high. Broil kabobs about 6 inches away from the heat source for 1-2 minutes until lightly charred on edges. Serve warm!
Notes
Hate peppers? Mix up the veggies with cut zucchini squash, mushrooms, and tomatoes.
Use metal skewers to avoid having to soak the wood, but either can be used.
If tolerated, red onion can be substituted for shallots, although I prefer the flavor of shallots.