Sirloin and Summer-Vegetable Kebabs with Chimichurri

INGREDIENTS

• 1 pound beef sirloin tips (cut into 1 1/2-inch pieces)
• 2 tablespoons plus 2 teaspoons balsamic vinegar
• 1 tablespoon soy sauce
• 1/4 teaspoon freshly ground pepper
• 1 medium zucchini
• 1 small yellow summer squash
• 1 onion
• 1 red bell pepper
• 1/2 cup chopped fresh flat-leaf parsley
• 1/2 cup chopped fresh oregano
• 2 minced garlic cloves
• 1/4 cup extra-virgin olive oil
• 2 teaspoons fresh lemon juice
• 3/4 teaspoon coarse salt