1 tablespoon freshly squeezed lemon juice from 1 lemon
1 tablespoon Dijon mustard
3 cloves garlic, minced
1 teaspoon dark brown sugar
2 teaspoons freshly ground black pepper
1½ pounds beef sirloin tips, cut into 1½-inch cubes
1 yellow bell pepper
1 red bell pepper, cut into 1½-inch squares
1 green bell pepper, cut into 1½-inch squares
1 zucchini, sliced thickly
1 small red onion, cut into 1½-inch squares
Instructions
Whisk together oil, Worcestershire, soy sauce, lemon juice, mustard, garlic, brown sugar, and black pepper in a small bowl. Place beef cubes and vegetables in a large resealable plastic bag. Add marinade and seal bag, pressing out as much air as possible. Marinate, refrigerated, for at least 1 and up to 5 hours.
Thread beef onto skewers, alternating with vegetables.
Clean and oil the grilling grate. Heat grill grate for 5 minutes.
Grill skewers until beef is well seared on all sides and center of beef registers between 125-130°F on an instant read thermometer, about 3 minutes per side. Transfer skewers to platter and let rest for 5 minutes. Serve immediately.
Recipe by Columbine Kitchen at https://columbinekitchen.com/?p=1824