- ¾ cup balsamic vinegar
- ¾ cup extra-virgin olive oil
- 2 tablespoons whole-grain mustard
- 1 tablespoon dried oregano
- 1 tablespoon dried rosemary
- 2 cloves garlic, sliced
- ½ teaspoon salt
- ½ teaspoon ground pepper
- 1 pound tri-tip sirloin steak, trimmed and cut into 32 chunks
- 16 button mushrooms
- 16 cherry tomatoes
- 1 small bell pepper (any color), cut into 16 pieces
- 16 (1 inch) chunks red onion
- Whisk vinegar, oil, mustard, oregano, rosemary, garlic, salt, and pepper together in a small bowl.
- Skewer beef, mushrooms, tomatoes, bell pepper pieces, and onion chunks, alternating evenly, on 8 metal or wooden skewers. Place the kebabs in a 9-by-13-inch baking dish and pour the marinade over them. Refrigerate (or store in a cooler packed with ice) for at least 2 hours and up to 8 hours (this should be done before leaving for the campground).
- Preheat grill to medium-high. Remove the kebabs from the dish; discard the marinade. Grill the kebabs, turning once, to desired doneness, 6 to 8 minutes total. To grill over your campfire, hold the skewers over the flames (but do not let the flames touch the food), turning regularly until the meat is cooked to your liking, about 15 minutes for medium.