Food roundup Supermarket situated in the entrance to the Yellowstone National park is well stocked and I found the prices to be very reasonable. They have most things that visitors to Yellowstone national park would need. They accept credit card even though it is small store that just caters to needs of the travelers. You can get some boxed fresh sandwiches to go. They have frozen dinners, bottled water, milk, yogurt and most popular snacks.