Ingredients: 
1 boneless beef top sirloin steak, cut 1-inch thick (about 1 1/4 pounds)
1 medium yellow squash, sliced (1/2-inch)
1 medium zucchini, sliced (1/2-inch)
1 small red onion, cut into 1/2-inch thick wedges
8 medium mushrooms
1 tablespoon Dijon-style mustard
1 tablespoon olive oil 
Mustard-Thyme Glaze:
2 tablespoons Dijon-style mustard
2 tablespoons apricot preserves
1 teaspoon fresh lemon juice
1/2 teaspoon dried thyme
1/4 teaspoon ground black pepper