diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index b2884b9c..570073c7 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -109,6 +109,7 @@ module ActiveModel
       end
     end
 
+    # @api private
     def self.serialization_adapter_instance
       @serialization_adapter_instance ||= ActiveModelSerializers::Adapter::Attributes
     end
@@ -138,9 +139,7 @@ module ActiveModel
     # associations, similar to how ActiveModel::Serializers::JSON is used
     # in ActiveRecord::Base.
     #
-    # TODO: Move to here the Attributes adapter logic for
-    # +serializable_hash_for_single_resource(options)+
-    # and include <tt>ActiveModel::Serializers::JSON</tt>.
+    # TODO: Include <tt>ActiveModel::Serializers::JSON</tt>.
     # So that the below is true:
     #   @param options [nil, Hash] The same valid options passed to `serializable_hash`
     #      (:only, :except, :methods, and :include).
@@ -164,10 +163,13 @@ module ActiveModel
     #     serializer.as_json(include: :posts)
     #     # Second level and higher order associations work as well:
     #     serializer.as_json(include: { posts: { include: { comments: { only: :body } }, only: :title } })
-    def serializable_hash(adapter_opts = nil)
-      adapter_opts ||= {}
-      adapter_opts = { include: '*' }.merge!(adapter_opts)
-      serialize(adapter_opts)
+    def serializable_hash(adapter_options = nil, options = {}, adapter_instance = self.class.serialization_adapter_instance)
+      adapter_options ||= {}
+      options[:include_directive] ||= ActiveModel::Serializer.include_directive_from_options(adapter_options)
+      cached_attributes = adapter_options[:cached_attributes] ||= {}
+      resource = cached_attributes(options[:fields], cached_attributes, adapter_instance)
+      relationships = resource_relationships(adapter_options, options, adapter_instance)
+      resource.merge(relationships)
     end
     alias to_hash serializable_hash
     alias to_h serializable_hash
@@ -199,15 +201,6 @@ module ActiveModel
       end
     end
 
-    # @api private
-    def serialize(adapter_options, options = {}, adapter_instance = self.class.serialization_adapter_instance)
-      options[:include_directive] ||= ActiveModel::Serializer.include_directive_from_options(adapter_options)
-      cached_attributes = adapter_options[:cached_attributes] ||= {}
-      resource = cached_attributes(options[:fields], cached_attributes, adapter_instance)
-      relationships = resource_relationships(adapter_options, options, adapter_instance)
-      resource.merge(relationships)
-    end
-
     # @api private
     def resource_relationships(adapter_options, options, adapter_instance)
       relationships = {}
@@ -227,7 +220,7 @@ module ActiveModel
       association_object = association_serializer && association_serializer.object
       return unless association_object
 
-      relationship_value = association_serializer.serialize(adapter_options, {}, adapter_instance)
+      relationship_value = association_serializer.serializable_hash(adapter_options, {}, adapter_instance)
 
       if association.options[:polymorphic] && relationship_value
         polymorphic_type = association_object.class.name.underscore
diff --git a/lib/active_model/serializer/collection_serializer.rb b/lib/active_model/serializer/collection_serializer.rb
index a2367195..bb84644c 100644
--- a/lib/active_model/serializer/collection_serializer.rb
+++ b/lib/active_model/serializer/collection_serializer.rb
@@ -11,22 +11,23 @@ module ActiveModel
         @object                  = resources
         @options                 = options
         @root                    = options[:root]
-        serializer_context_class = options.fetch(:serializer_context_class, ActiveModel::Serializer)
-        @serializers = resources.map do |resource|
-          serializer_class = options.fetch(:serializer) { serializer_context_class.serializer_for(resource) }
-
-          if serializer_class.nil? # rubocop:disable Style/GuardClause
-            fail NoSerializerError, "No serializer found for resource: #{resource.inspect}"
-          else
-            serializer_class.new(resource, options.except(:serializer))
-          end
-        end
+        @serializers             = serializers_from_resources
       end
 
       def success?
         true
       end
 
+      # @api private
+      def serializable_hash(adapter_options, options, adapter_instance)
+        include_directive = ActiveModel::Serializer.include_directive_from_options(adapter_options)
+        adapter_options[:cached_attributes] ||= ActiveModel::Serializer.cache_read_multi(self, adapter_instance, include_directive)
+        adapter_opts = adapter_options.merge(include_directive: include_directive)
+        serializers.map do |serializer|
+          serializer.serializable_hash(adapter_opts, options, adapter_instance)
+        end
+      end
+
       # TODO: unify naming of root, json_key, and _type.  Right now, a serializer's
       # json_key comes from the root option or the object's model name, by default.
       # But, if a dev defines a custom `json_key` method with an explicit value,
@@ -56,19 +57,28 @@ module ActiveModel
           object.respond_to?(:size)
       end
 
-      # @api private
-      def serialize(adapter_options, options, adapter_instance)
-        include_directive = ActiveModel::Serializer.include_directive_from_options(adapter_options)
-        adapter_options[:cached_attributes] ||= ActiveModel::Serializer.cache_read_multi(self, adapter_instance, include_directive)
-        adapter_opts = adapter_options.merge(include_directive: include_directive)
-        serializers.map do |serializer|
-          serializer.serialize(adapter_opts, options, adapter_instance)
-        end
-      end
-
       protected
 
       attr_reader :serializers, :options
+
+      private
+
+      def serializers_from_resources
+        serializer_context_class = options.fetch(:serializer_context_class, ActiveModel::Serializer)
+        object.map do |resource|
+          serializer_from_resource(resource, serializer_context_class, options)
+        end
+      end
+
+      def serializer_from_resource(resource, serializer_context_class, options)
+        serializer_class = options.fetch(:serializer) { serializer_context_class.serializer_for(resource) }
+
+        if serializer_class.nil? # rubocop:disable Style/GuardClause
+          fail NoSerializerError, "No serializer found for resource: #{resource.inspect}"
+        else
+          serializer_class.new(resource, options.except(:serializer))
+        end
+      end
     end
   end
 end
diff --git a/lib/active_model_serializers/adapter/attributes.rb b/lib/active_model_serializers/adapter/attributes.rb
index 3d2e7b52..f28295c0 100644
--- a/lib/active_model_serializers/adapter/attributes.rb
+++ b/lib/active_model_serializers/adapter/attributes.rb
@@ -3,7 +3,7 @@ module ActiveModelSerializers
     class Attributes < Base
       def serializable_hash(options = nil)
         options = serialization_options(options)
-        serializer.serialize(instance_options, options, self)
+        serializer.serializable_hash(instance_options, options, self)
       end
     end
   end