Note: I don't know if this feature is available in all areas so it may be YMMV.
Also, if you are not aware Walmart Grocery can be used for many items besides groceries.
For example some of the current Walmart items on Slickdeals front page can be used for this.
Order online. Pick up in store.
They changed it to $10 off $50 for just the first purchase (new customer) with the new ad. 8/12 -8/30 $10 off $50 each of your first 3 orders
*Valid only for your first purchase at Walmart Grocery online service. Discount applies to 3 separate orders; minimum order of $50. Subsequent orders must be placed within 60 days of 1st discounted order. Customer must enter code with each order. Only one discount code per order. Does not apply to alcohol purchases. Customer responsible for all applicable taxes. Promotion code expires 9/30/18.