Got it working! This worked for me after making sure the drive was changed to GPT and I also labeled the efi parition as “EFI”:
menuentry “Windows” {
insmod chain
insmod ntfs
insmod part_gpt
set root=(hd1,gpt2)
chainloader (hd1,gpt2)/efi/microsoft/boot/bootmgfw.efi
}

Just realized that the set root part is redundant. I am partitoning the drive now to copy the files from the FOG USB key then tell the UEFI on the PC to boot from this new GRUB partition first. Looking good!

I copied all the files with the folder structure to the partition I created. Set the part type to EFI System, filesystem to FAT32, told the BIOS/UEFI to boot from bootx64.efi in /BOOT/EFI and landed at a grub rescue prompt. After playing out the process in my head I realize that full automation won’t work because the way the menu is set up to autoboot into Windows after 5 seconds will prevent a deploy or capture task from ever starting. I’d have to be at the PC to select the Deploy/Capture option on the FOG Menu. The USB option still works though so all is not lost.

Got it working! This worked for me after making sure the drive was changed to GPT and I also labeled the efi parition as “EFI”:
menuentry “Windows” {
insmod chain
insmod ntfs
insmod part_gpt
set root=(hd1,gpt2)
chainloader (hd1,gpt2)/efi/microsoft/boot/bootmgfw.efi
}

Just realized that the set root part is redundant. I am partitoning the drive now to copy the files from the FOG USB key then tell the UEFI on the PC to boot from this new GRUB partition first. Looking good!

that didnt work for me. said ntldr and drivemap not a command.

I found the Windows partition it is actually (hd1,msdos1). I ran "ls (hd1,msdos1) and it showed filesystem ntfs label “Windows” and the UUID. But when I try to run the command “chainloader (hd1,msdos1)/EFI/Microsoft/Boot/bootmgfw.efi” or “chainloader (hd1,msdos1)/EFI/Microsoft/Boot/bootx64.efi”, says file not found.

Correction: This drive was MBR with only one partition. Sorry about that.

It probably is the USB drive. I don’t think this particular environment is seeing the hard drive in the PC. I know for a fact that the Windows drive is GPT and EFI because I converted it to GPT before I imaged it, also made sure the image itself was created as GPT. I am able to boot from the Windows EFI partition normally.

@Sebastian-Roth The windows partition I’m trying to boot from is a GPT-EFI bootable system. Is that “+1” always supposed to follow the chainloader entry?

Great thanks! I already found and tried this:
insmod part_gpt
insmod chain
set root=(hd0,gpt1)
chainloader /EFI/Microsoft/Boot/bootmgfw.efi
boot

No luck. Says the file could not be found.

The ls command shows hd0 hd0,msdos hd1 hd1,msdos, hd2 hd2, msdos. I tried all three hd entries and pointed to /EFI/Microsoft/Boot/bootmgfw.efi no go, but much further than I was thanks to you and @george1421.

UPDATE!!!
I added a storage node and specified the interface and ip of my prod network and successfully deployed an image using the USB FOG. Now I added an entry to the GRUB menu called “Boot from HDD” but I don’t know the command line to boot from it. I have used “sanboot --no-describe --drive 0x08” in an ipxe menu file with a different setup but GRUB isn’t recognizing sanboot.