1. Press dressing mix evenly onto all surfaces of beef pot roast. Place onions and garlic in 4-1/2 to 5-1/2-quart slow cooker; top with pot roast. Add bell peppers and broth. Cover and cook on HIGH 5 hours or on LOW 8 hours. Add zucchini. Continue cooking, covered, 30 minutes or until pot roast is fork-tender.
2. Remove pot roast and vegetables. Combine 2 cups cooking liquid and cornstarch mixture in medium saucepan. Bring to a boil, stirring constantly; cook and stir 1 minute or until thickened.
3. Slice roast; season with salt and pepper, as desired. Serve topped with sauce.
TIP: Always use grass-fed beef. The fat content is so low, you will not have to separate the fat from the au jus (broth) before making your sauce.