Combine olive oil, balsamic vinegar, minced garlic, fresh rosemary, fresh thyme, salt, black pepper, Dijon mustard, honey, and paprika in a large mixing bowl. Whisk until well blended, creating an emulsified marinade that will coat every piece of meat evenly.

Add your beef cubes to the marinade and toss thoroughly to coat all surfaces. Cover the bowl with plastic wrap and refrigerate for at least 15 minutes, though 30 minutes yields deeper flavor development and more tender results.

While beef marinates, soak wooden skewers in water for 20 minutes to prevent burning, or use metal skewers for reusable convenience. Prepare your vegetables by cutting bell peppers and red onion into similar-sized chunks to match the beef cubes for even cooking throughout.

Thread cozy labor day beef kebabs recipe onto skewers by alternating beef cubes with peppers, onion, and mushrooms in an appealing pattern. Leave slight gaps between ingredients to allow heat circulation and even cooking, rather than packing them tightly together.

Preheat your grill to medium-high heat, approximately 400°F, and brush grates with oil to prevent sticking. Grill kebabs for 15-20 minutes, rotating every 3-4 minutes to ensure even charring and cooking on all sides without burning the vegetables.

The beef should reach an internal temperature of 145°F for medium-rare doneness; use an instant-read thermometer for accuracy. Remove from heat and let rest for 3-5 minutes before serving to allow juices to redistribute throughout the meat.