2 medium orange, red and /or yellow bell peppers, sliced
1/2 medium head of cauliflower, cut into small florets (about 2 cups)
4 sirloin strip steaks (about 6 ounces each)
1/2 teaspoon salt
In medium bowl, whisk together oil, vinegar, brown sugar and steak seasoning. Place vegetables in large zip-top plastic bag; pour half the marinade into bag. Place 2 steaks in each of 2 large zip-top plastic bags; pour half the remaining marinade into each bag. Seal bags, pressing out extra air; refrigerate at least 1 hour or up to 4 hours.
Prepare grill for direct grilling over medium-high heat. Place four 12-inch square sheets of aluminum foil on work surface. With slotted spoon, evenly divide vegetables onto center of each foil sheet; sprinkle vegetables with salt. For each packet, bring top and bottom sides of foil together over vegetables; crimp together and fold down over vegetables. Double fold both ends of packets toward vegetables.
Remove steaks from marinade; discard marinade. Place steaks and packets on hot grill rack. Cook steaks, covered, 6 to 8 minutes or until grill marks appear and internal temperature reaches 135°, turning once halfway through cooking; cook packets 12 minutes, turning once halfway through cooking. Transfer steak to cutting board; let steak stand 10 minutes. Internal temperature will rise to 145° upon standing for medium-rare.
To serve, slice steak across the grain and serve with vegetables.