Hi NCVA,
The detailed steps for creating a distribution group (not a Group contact) in OWA are as below for your reference.
1. Login to OWA with your account at http://mail.office365.com.
2. Click Options at the right corner on the top, and then select See All Options.
3. Click Groups on the left panel, and then you can create a new distribution group by clicking New… under Public Groups I Own. My screenshot shows as follows.
In addition, the article Create a New Distribution Group I provided previously introduces the detailed steps to create a distribution group in the Exchange Online Control Panel (ECP). Either creating the distribution group in OWA or in ECP by performing the correct methods, the distribution group contact is stored in the Global Address List (shared address book ), the group is counted as one recipient when sending emails to the group.
Thanks,
Maggie Li