Place the corned beef brisket in a 5-6 quart slow cooker along with the peeled and chunked carrots, parsnips, frozen pearl onions, chopped parsley, bay leaves, peppercorns, and 3 cups of water.
Cover the crock pot and set it to cook on high for 4 hours to allow the flavors to meld and meat to tenderize.
After 4 hours, add the cabbage wedges to the slow cooker and continue cooking on high for an additional 1 hour and 20 minutes until the cabbage is soft and cooked through.
Carefully remove the corned beef from the crock pot and let it rest for 5 minutes before slicing into pieces.
Serve the sliced corned beef with the cooked vegetables alongside cauliflower puree or buttermilk mashed potatoes, and enjoy your delicious meal!