Simply use OpenStruct#to_h to receive an OpenStruct's hash representation.
In older Rubies you need OpenStruct#marshal_dump instead.

Ruby 2.0+

>> OpenStruct.new(foo: 23, bar: 42).to_h
=> { :foo => 23, :bar => 42 }

Ruby 1.9.3 and 1.8.7

>> OpenStruct.new(:foo => 23, :bar => 42).marshal_dump
=> { :foo => 23, :bar => 42 }

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

• Prevents you from data breaches and liability risks
• Upgrade at your own pace
• Works with modern Rubies

Read more Show archive.org snapshot

Both approaches will return the underlying hash table (a clone of it in Ruby 2.0+).