There isn't any pre-defined report that will show us who and how many registered, but you can run a Query based on Interaction type and subject.
  1. Go to Data Management > select Query
  2. Click Create a new Query
  3. Give the Query a name, Description and Security Category
  4. Click Save
  5. You'll land on the Query Builder tab
  6. Click the "Add an Interaction Clause" button
  7. Select Default Types as the Interaction Group
  8. Select Contact Record Change as the Interaction Type
  9. Next to "With subject:" type "QuickReg"
  10. Click Save
  11. Click Save Query
  12. Click Run Query
You will be given a list of constituents that registered using QuickReg. You can export these results in to a CSV by following the instructions in the link below.

To use query results to create a Mail-Merge List (external CSV file)