Its not quite as easy as editing grub.cfg or at least it wasn't for me.
Warning: I take no responsibility if you hose your machine. This worked for me but do this at your own risk. I would make sure to back up your current grub.cfg file before you start messing with this.
You have to make your own menu at /etc/grub.d/40_custom. What I did was copied all of the entries out of /boot/grub/grub.cfg and pasted them into /etc/grub.d/40_custom. An entry begins with "menuentry" and ends with " } " Put them in the order you want them there and fix the entries as you deem fit. Then you need to change the permissions on /etc/grub.d/10_linux and /etc/grub.d/30_os-prober. The code is as follows:
I left the memtest stuff but you dont have too. If you dont want them be sure to add /etc/grub.d/20_memtest86+ to the command above. Once you have done this you need do a update-grub in terminal. I would check your grub file after this and make sure you see all your entries are in your /boot/grub/grub.cfg file otherwise you may not have anything in the list when you restart. If nothing is in the list you did something wrong.
chmod -x /etc/grub.d/10_linux /etc/grub.d/30_os-prober
This will likely only fix the issue until another kernel update. Then you will have a new entry and have to modify the order again. I hope this helps and let me know if you have any issues and I will try to help to the best of my knowledge.