Wash the potatoes and onions. Chop the potatoes and onions into large chunks.
Place the potatoes, onion, and baby carrots into an oven safe casserole dish and then place brisket with the fat side up on the vegetables.
In a medium sized bowl combine the onion soup mix, ketchup, and ginger ale. Pour over the brisket and vegetables.
Cover the casserole dish with tinfoil and bake for 3 to 3 and 1/2 hours. Remove the foil and bake for the last half hour if desired.
Carefully remove the casserole dish from the oven. Remove the brisket from the casserole dish and trim off the fat from the top. Cut up the brisket as desired and then return to the casserole dish to get it covered in the sauce.