I love Quests. The big Quests on your left hand side with the timer are probably the easiest aspect of Gourmet Ranch. You should see some variation of this on your left hand side of your ranch.
Usually the dishes are high value. You do not need to cook or even grow ANY of the ingredients. You can buy everything dishes, ingredients from a neighbor. The more you buy the more experience you receive. And of course once you have completed the Quest you will receive speedups and GR cash.
Here is a quick snapshot of a current quest. As you can see you need 106 of each dish. The prizes are 20 speedups, 50 speedups and 10 GR cash. And as you can see there is a nifty little counter down at the bottom.
Ideally you want to be able to unlock some of the ingredients to grow so you can cook them throughout the year but if you can't try to grow some of the regulars for the Quest and trade them for the high value supers. That will allow your neighbors to not have to worry about the regular ingredients and they can grow more of the supers. The more they are able to grow, the more they are able to share.
Click on the BAKE NOW button to bring up a snapshot of the dish and the required ingredients.
Here is the first dish. As you can see I have the first ingredient but not the second two. I have two options I can grow them as I have both unlocked.
My second option is to click on Check Neighbors. From here you can see that Big Mart has it for sale for GR cash. Or I have four neighbors that have pumpkins for sale for coins.
There is also the option to GIFT quest dishes to your neighbors.
This is your gift box icon if you click on it, it will bring up a second screen.
And you can see the first three dishes are the quest dishes. Ideally you want to send the top dish available. Its free money! I would not expect to complete a quest based on free gifts alone. However it certainly could be a few extra thousand coins and when you are lower level, every single coin matters.