Default OS after Fedora installation

1.
grep menuentry /boot/grub2/grub.cfg
This will display all your grub entries

Highlight the entry you want to default to - for example Windows 7 (loader) (on /dev/sda1) Right click and choose copy

Type

2.
vi /etc/default/grub
Change the entry

GRUB_DEFAULT=0
to

GRUB_DEFAULT="Windows 7 (loader) (on /dev/sda1)"
i.e. paste the entry you want (including the quotes)

Save, then type

PS: Having this "Windows 7 (loader) (on /dev/sda1)" is enough.

2.
grub2-mkconfig -o /boot/grub2/grub.cfg

thats it and this worked for me.

Source: https://ask.fedoraproject.org/en/question/8885/how-can-i-change-default-operating-system-in-start-up-boot-menu/