1. Preheat oven to 350°. Stir together first 3 ingredients and both envelopes from soup mix package in a large bowl.
2. Place brisket, fat side up, in an aluminum foil-lined roasting pan. Pour chili sauce mixture over brisket.
3. Bake, tightly covered, at 350° for 4 to 4 1/2 hours or until fork-tender. Remove from oven; let stand 20 minutes. Cut brisket across the grain into thin slices using a sharp knife, and pour pan juices over slices.
Note: We tested with Lipton Kosher Recipe Secrets Onion Recipe Soup & Dip Mix.