Pour 1 jar of Bistro Au Jus Sauce into the Slow Cooker (Crock Pot).
Add the deli roast beef slices one at a time so they cook evenly in the Slow Cooker (Crock Pot).
Add in these sliced onions and chopped garlic.
Add the second jar of Bistro Au Jus Sauce on top of all the ingredients.
Cook on low for 2 - 2 1/2 hours on low.