Hi Bill,
You can do just that, by using EntityQuery with TypeName = Task specifying a condition on the Project field with the In operator and a QueryExpression _for that Project field in the _RightExpression.
You can find a sample for the use of In operator in this post:
https://success.clarizen.com/entries/38249296-Query-ResourceLinks-for-All-WorkItems-of-type-Task
Hope this helps,
Ophir