- 1 1/2 pounds sirloin steak, (about 1 1/4 inches thick)
- 24 grape tomatoes
- 2 tablespoons olive oil, plus more for grill
- 2 tablespoons grainy mustard
- 1 tablespoon red-wine vinegar
- 1 tablespoon dried thyme leaves
- Coarse salt and ground pepper
- Slice beef into cubes. Assemble 4 long skewers, alternating 5 beef cubes (threaded perpendicular to the cut) with 6 grape tomatoes on each. Arrange skewers in a nonmetallic dish.
- In a small bowl, whisk together oil, mustard, vinegar, and thyme. Pour marinade over skewers; turn to coat. Cover and let stand at least 2 hours in the refrigerator, turning periodically.
- Heat grill to high and lightly oil grates.
- Season skewers with salt and pepper and place them on grill. Cover grill and cook, turning occasionally, until grill marks are visible and meat is cooked to desired doneness, 1 to 2 minutes per side for medium rare.