Sprinkle steak with 1/4 teaspoon salt and 1/4 teaspoon black pepper.
Combine 1/2 teaspoon of salt, 1/4 teaspoon of black pepper, vinegar, and next 5 ingredients (through garlic) in a large zip-top plastic bag. Seal and shake to coat.
Place steak on grill rack or broiler pan coated with cooking spray; cook 4 minutes on each side or until desired degree of doneness.
Let stand 5 minutes; cut steak into 1/4-inch slices.
Place zucchini and squash on grill rack or broiler pan coated with cooking spray; cook for 4 minutes on each side or until tender.
Place bell peppers and onions on grill rack or broiler pan; cook 2 minutes or just until tender.
