Yes, you can deploy resources in a blueprint definition to an existing resource group. Some caveats though:
- If the resource group exists, the artifact definition of the resource group in the blueprint definition must also match the location. If the location for that RG in the blueprint definition is different than the existing RG's location, the blueprint assignment will fail.
- The existing resource group can't be locked. If the blueprint definition adds a tag to the resource group and the resource group is set to blueprint locking "Read Only", the assignment will fail. If the blueprint definition doesn't alter the resource group, you can still add "Not Locked" resources to a Read Only resource group. For more information, see Blueprint locks.
You can hard wire the resource group name/location on the blueprint definition or set it at assignment time to something that already exists. Either way, make sure it meets the above two criteria. Another way is to use an ARM template artifact at the subscription level that targets resources to an existing RG.