Default Opportunity Team Role where Opportunity Access = "Owner"

I am attempting to default the "Team Role" value, on an Opportunity Team record to "Account Executive", when new opportunities are created. Currently, the Opportunity Owner is added to the team, however the "Team Role" value must be manually added, after initially saving the opportunity. This is causing unnecessary steps for our users and needs to be automated.
I've tried setting the Default Value at the "Team Role" field, itself, on the Opportunity Team record-type, using the following syntax:
IIf([<OpportunityAccess>]="Owner","Account Executive","")

I've also tried a workflow (When Record Is Saved), with a Wait-action and then a field-update action.