With the addition of some staples, like bread, rice, butter, cheese, milk, pasta, etc., a garden can happily replace almost any produce you'd usually pick up from the store. With some replacements, you can cook an entire meal simply from the fruits of your garden's labor. The best part about greenhouses, besides the obvious bountiful veggies and fruits, you can grow herbs for seasoning these veggies into fulfilling meals.
You may still need a few things from grocery stores. Keeping a steady supply of dairy products (if you consume dairy) could be useful. Becoming vegan would be the best way to completely give up groceries. However, that isn't exactly realistic, especially to families that have eaten meat and dairy products.
