I see below option, never tested though.
root@Router-2# set interfaces gr-0/0/0 unit 0 copy-tos-to-outer-ip-header ?
Possible completions:
<[Enter]> Execute this command
accounting-profile Accounting profile name
+ apply-groups Groups from which to inherit configuration data
+ apply-groups-except Don't inherit configuration data from these groups
> backup-options Backup interface configuration options
bandwidth Logical unit bandwidth (informational only)
clear-dont-fragment-bit Clear DF bit in packet (AS PIC and J-series only)
copy-tos-to-outer-ip-header Copy IP payload header's ToS field to GRE delivery header
description Text description of interface
disable Disable this logical interface
encapsulation Logical link-layer encapsulation
> family Protocol family
no-traps Don't enable SNMP notifications on state changes
point-to-point Point-to-point connection
> ppp-options Point-to-Point Protocol interface-specific options
> radio-router Parameters for dynamic link cost management
traps Enable SNMP notifications on state changes
> tunnel Tunnel parameters
| Pipe through a command