This feature was added in https://github.com/mongoid/mongoid/pull/678

X.find_or_initialize_by(a: a, b: b, c: c) do |x|
  puts x
end

It only runs through the block on initialize (or create, if find_or_create_by is used).

The related code in finders.rb is

def find_or(method, attrs = {}, &block)
  first(:conditions => attrs) || send(method, attrs, &block)
end

Shouldn't the block variable pass on to the finder as well?