Modification of boot time (grub timeout) is little different in rhel 7. Grub timeout is time to wait for manual selection of boot entry loaded by GRUB boot loader. This is useful for maintenance boot or to edit/modify boot entry In rhel 7 default grub timeout is 5 second.
In rhel 7 /boot/grub directory is not present nor /boot/grub/menu.list. In rhel 7 grub is modified with grub2 and we can use /etc/default/grub file to modify boot loader configuration.
It’s not recommended to modify any grub file in rhel 7 apart from /etc/default/grub.
Following are the default values from /etc/default/grub file.