1 cup frozen broccoli-cauliflower blend, thawed and chopped
1/2 cup grated Parmesan cheese, divided
Cook orzo according to package directions; drain. Cut and discard tops from peppers; remove seeds. Place in a 3-qt. round microwave-safe dish. Add water; microwave, covered, on high until peppers are crisp-tender, 7-9 minutes.
In a large skillet, cook and crumble beef with onion over medium heat until no longer pink, 5-7 minutes; drain. Stir in pasta sauce, vegetables, 1/4 cup cheese and orzo. Spoon into peppers. Sprinkle with remaining cheese.
Microwave, uncovered, on high until heated through, 1-2 minutes.