diff --git a/app/controllers/assignments_api_controller.rb b/app/controllers/assignments_api_controller.rb
index 7fa60da5edf..b5c2731cca0 100644
--- a/app/controllers/assignments_api_controller.rb
+++ b/app/controllers/assignments_api_controller.rb
@@ -61,6 +61,29 @@
 #       // Turnitin plugin available
 #       turnitin_enabled: true,
 #
+#       // Settings to pass along to turnitin to control what kinds of matches
+#       // should be considered.
+#       // originality_report_visibility can be 'immediate', 'after_grading', or 'after_due_date'
+#       // exclude_small_matches_type can be null, 'percent', 'words'
+#       // exclude_small_matches_value:
+#       // - if type is null, this will be null also
+#       // - if type is 'percent', this will be a number between 0 and 100
+#       //   representing match size to exclude as a percentage of the document size.
+#       // - if type is 'words', this will be number > 0 representing how many
+#       //   words a match must contain for it to be considered
+#       // NOTE: This flag will not appear unless your account has the
+#       // Turnitin plugin available
+#       turnitin_settings: {
+#         originality_report_visibility => 'after_grading',
+#         s_paper_check => false,
+#         internet_check => false,
+#         journal_check => false,
+#         exclude_biblio => false,
+#         exclude_quoted => false,
+#         exclude_small_matches_type => 'percent',
+#         exclude_small_matches_value => 50,
+#       },
+#
 #       // If this is a group assignment, boolean flag indicating whether or
 #       // not students will be graded individually.
 #       grade_group_students_individually: false,
@@ -71,9 +94,9 @@
 #       // Use the "External Tools" API if you need more information about
 #       // an external tool.
 #       external_tool_tag_attributes: {
-#         // URL to the external tool \ 
+#         // URL to the external tool
 #         url: "http://instructure.com",
-#         // Whether or not there is a new tab for the external tool\ 
+#         // Whether or not there is a new tab for the external tool
 #         new_tab: false
 #       },
 #       
@@ -269,6 +292,10 @@ class AssignmentsApiController < ApplicationController
   #   Toggles Turnitin submissions for the assignment.
   #   Will be ignored if Turnitin is not available for the course.
   #
+  # @argument assignment[turnitin_settings] [Optional]
+  #   Settings to send along to turnitin. See Assignment object definition for
+  #   format.
+  #
   # @argument assignment[peer_reviews] [Optional,Boolean]
   #   If submission_types does not include external_tool,discussion_topic,
   #   online_quiz, or on_paper, determines whether or not peer reviews
diff --git a/app/models/account.rb b/app/models/account.rb
index 1279f48a4a8..86b65538d89 100644
--- a/app/models/account.rb
+++ b/app/models/account.rb
@@ -871,7 +871,7 @@ class Account < ActiveRecord::Base
   end
   
   def turnitin_settings
-    if self.turnitin_account_id && self.turnitin_shared_secret && !self.turnitin_account_id.empty? && !self.turnitin_shared_secret.empty?
+    if self.turnitin_account_id.present? && self.turnitin_shared_secret.present?
       [self.turnitin_account_id, self.turnitin_shared_secret]
     else
       self.parent_account.turnitin_settings rescue nil
diff --git a/app/models/assignment.rb b/app/models/assignment.rb
index 6daf8ac427c..50a146d16b2 100644
--- a/app/models/assignment.rb
+++ b/app/models/assignment.rb
@@ -312,10 +312,6 @@ class Assignment < ActiveRecord::Base
     end
   end
 
-  def turnitin_enabled?
-    self.turnitin_enabled
-  end
-
   attr_accessor :updated_submissions
   def update_submissions_later
     if @old_assignment_group_id != self.assignment_group_id
diff --git a/lib/api/v1/assignment.rb b/lib/api/v1/assignment.rb
index 06d2fd70e6d..8d58fd36b92 100644
--- a/lib/api/v1/assignment.rb
+++ b/lib/api/v1/assignment.rb
@@ -71,6 +71,7 @@ module Api::V1::Assignment
 
     if assignment.context && assignment.context.turnitin_enabled?
       hash['turnitin_enabled'] = assignment.turnitin_enabled
+      hash['turnitin_settings'] = turnitin_settings_json(assignment)
     end
 
     if assignment.rubric_association
@@ -108,6 +109,25 @@ module Api::V1::Assignment
     hash
   end
 
+  def turnitin_settings_json(assignment)
+    settings = assignment.turnitin_settings.with_indifferent_access
+    [:s_paper_check, :internet_check, :journal_check, :exclude_biblio, :exclude_quoted].each do |key|
+      settings[key] = value_to_boolean(settings[key])
+    end
+
+    ex_type = settings.delete(:exclude_type)
+    settings[:exclude_small_matches_type] = case ex_type
+      when '0'; nil
+      when '1'; 'words'
+      when '2'; 'percent'
+    end
+
+    ex_value = settings.delete(:exclude_value)
+    settings[:exclude_small_matches_value] = ex_value.present? ? ex_value.to_i : nil
+
+    settings.slice(*API_ALLOWED_TURNITIN_SETTINGS)
+  end
+
   API_ALLOWED_ASSIGNMENT_INPUT_FIELDS = %w(
     name
     description
@@ -127,6 +147,18 @@ module Api::V1::Assignment
     grade_group_students_individually
     set_custom_field_values
     turnitin_enabled
+    turnitin_settings
+  )
+
+  API_ALLOWED_TURNITIN_SETTINGS = %w(
+    originality_report_visibility
+    s_paper_check
+    internet_check
+    journal_check
+    exclude_biblio
+    exclude_quoted
+    exclude_small_matches_type
+    exclude_small_matches_value
   )
 
   def update_api_assignment(assignment, assignment_params, save = true)
@@ -137,24 +169,44 @@ module Api::V1::Assignment
       update_params["submission_types"] = update_params["submission_types"].join(',')
     end
 
-    if assignment_params.has_key?("assignment_group_id")
-      ag_id = assignment_params["assignment_group_id"]
-      if ag_id.nil? || ag_id.is_a?( Numeric )
-        assignment.assignment_group = assignment.context.assignment_groups.find_by_id(ag_id)
-      end
+    # validate and add to update_params
+    if update_params.has_key?("assignment_group_id")
+      ag_id = update_params.delete("assignment_group_id").presence
+      ag = assignment.context.assignment_groups.find_by_id(ag_id)
+      update_params["assignment_group_id"] = ag.try(:id)
     end
 
-    if assignment_params.has_key?("group_category_id")
-      gc_id = assignment_params["group_category_id"]
-      if gc_id.nil? || gc_id.is_a?( Numeric )
-        assignment.group_category = assignment.context.group_categories.find_by_id(gc_id)
-      end
+    # validate and add to update_params
+    if update_params.has_key?("group_category_id")
+      gc_id = update_params["group_category_id"].presence
+      gc = assignment.context.group_categories.find_by_id(gc_id)
+      update_params["group_category_id"] = gc.try(:id)
     end
 
+    # do some fiddling with due_at for fancy midnight and add to update_params
     if update_params.has_key?("due_at")
       update_params["time_zone_edited"] = Time.zone.name
-      # do some fiddling with due_at for fancy midnight
       assignment.due_at = update_params["due_at"]
+      update_params["due_at"] = assignment.due_at
+    end
+
+    if !assignment.context.try(:turnitin_enabled?)
+      update_params.delete("turnitin_enabled")
+      update_params.delete("turnitin_settings")
+    end
+
+    # use Assignment#turnitin_settings= to normalize, but then assign back to
+    # hash so that it is written with update_params
+    if update_params.has_key?("turnitin_settings")
+      turnitin_settings = update_params["turnitin_settings"].slice(*API_ALLOWED_TURNITIN_SETTINGS)
+      turnitin_settings['exclude_type'] = case turnitin_settings['exclude_small_matches_type']
+        when nil; '0'
+        when 'words'; '1'
+        when 'percent'; '2'
+      end
+      turnitin_settings['exclude_value'] = turnitin_settings['exclude_small_matches_value']
+      assignment.turnitin_settings = turnitin_settings
+      update_params["turnitin_settings"] = assignment.turnitin_settings
     end
 
     # TODO: allow rubric creation
diff --git a/lib/turnitin.rb b/lib/turnitin.rb
index f3414f34e08..816cb44a891 100644
--- a/lib/turnitin.rb
+++ b/lib/turnitin.rb
@@ -120,7 +120,8 @@ module Turnitin
         settings[:originality_report_visibility] = 'immediate' unless ['immediate', 'after_grading', 'after_due_date'].include?(settings[:originality_report_visibility])
 
         [:s_paper_check, :internet_check, :journal_check, :exclude_biblio, :exclude_quoted].each do |key|
-          settings[key] = '0' unless settings[key] == '1'
+          bool = Canvas::Plugin.value_to_boolean(settings[key])
+          settings[key] = bool ? '1' : '0'
         end
 
         exclude_value = settings[:exclude_value].to_i
diff --git a/spec/apis/v1/assignments_api_spec.rb b/spec/apis/v1/assignments_api_spec.rb
index 14b23bc2e4c..dec5943d3f1 100644
--- a/spec/apis/v1/assignments_api_spec.rb
+++ b/spec/apis/v1/assignments_api_spec.rb
@@ -195,10 +195,19 @@ describe AssignmentsApiController, :type => :integration do
       @json['position'].should == 1
       @json['group_category_id'].should == @group_category.id
       @json['turnitin_enabled'].should == true
+      @json['turnitin_settings'].should == {
+        'originality_report_visibility' => 'immediate',
+        's_paper_check' => true,
+        'internet_check' => true,
+        'journal_check' => true,
+        'exclude_biblio' => true,
+        'exclude_quoted' => true,
+        'exclude_small_matches_type' => nil,
+        'exclude_small_matches_value' => nil
+      }
       @json['allowed_extensions'].should =~ [
         'docx','ppt'
       ]
-      @json['turnitin_enabled'].should == true
       @json['points_possible'].should == 12
       @json['grading_type'].should == 'points'
       @json['due_at'].should == @assignment.due_at.iso8601
@@ -341,10 +350,10 @@ describe AssignmentsApiController, :type => :integration do
           'points_possible' => '12',
           'assignment_group_id' => @group.id,
           'set_custom_field_values' => {
-          'test_custom' => {
-          'value' => '1'
-        }
-        },
+            'test_custom' => {
+              'value' => '1'
+            }
+          },
           'group_category_id' => nil,
           'description' => 'assignment description',
           'grading_type' => 'points',
@@ -428,7 +437,6 @@ describe AssignmentsApiController, :type => :integration do
       it "updates custom fields" do
         @assignment.get_custom_field_value('test_custom').true?.should == true
       end
-
     end
 
     context "when updating assignment overrides on the assignment" do
@@ -480,6 +488,78 @@ describe AssignmentsApiController, :type => :integration do
       end
     end
 
+    context "when turnitin is enabled on the context" do
+      before do
+        course_with_teacher(:active_all => true)
+        @assignment = @course.assignments.create!
+        acct = @course.account
+        acct.turnitin_account_id = 0
+        acct.turnitin_shared_secret = "blah"
+        acct.save!
+      end
+
+      it "should allow setting turnitin_enabled" do
+        @assignment.should_not be_turnitin_enabled
+        api_update_assignment_call(@course,@assignment,{
+          'turnitin_enabled' => '1',
+        })
+        @assignment.reload.should be_turnitin_enabled
+        api_update_assignment_call(@course,@assignment,{
+          'turnitin_enabled' => '0',
+        })
+        @assignment.reload.should_not be_turnitin_enabled
+      end
+
+      it "should allow setting valid turnitin_settings" do
+        update_settings = {
+          :originality_report_visibility => 'after_grading',
+          :s_paper_check => '0',
+          :internet_check => false,
+          :journal_check => '1',
+          :exclude_biblio => true,
+          :exclude_quoted => '0',
+          :exclude_small_matches_type => 'percent',
+          :exclude_small_matches_value => 50
+        }
+
+        json = api_update_assignment_call(@course, @assignment, {
+          :turnitin_settings => update_settings
+        })
+        json["turnitin_settings"].should == {
+          'originality_report_visibility' => 'after_grading',
+          's_paper_check' => false,
+          'internet_check' => false,
+          'journal_check' => true,
+          'exclude_biblio' => true,
+          'exclude_quoted' => false,
+          'exclude_small_matches_type' => 'percent',
+          'exclude_small_matches_value' => 50
+        }
+
+        @assignment.reload.turnitin_settings.should == {
+          'originality_report_visibility' => 'after_grading',
+          's_paper_check' => '0',
+          'internet_check' => '0',
+          'journal_check' => '1',
+          'exclude_biblio' => '1',
+          'exclude_quoted' => '0',
+          'exclude_type' => '2',
+          'exclude_value' => '50'
+        }
+      end
+
+      it "should not allow setting invalid turnitin_settings" do
+        update_settings = {
+          :blah => '1'
+        }.with_indifferent_access
+
+        api_update_assignment_call(@course, @assignment, {
+          :turnitin_settings => update_settings
+        })
+        @assignment.reload.turnitin_settings["blah"].should be_nil
+      end
+    end
+
     context "when a non-admin tries to update a completely frozen assignment" do
       it "doesn't allow the non-admin to update the frozen assignment" do
         course_with_teacher(:active_all => true)
diff --git a/spec/models/assignment_spec.rb b/spec/models/assignment_spec.rb
index 8324fd69833..b3e87471640 100644
--- a/spec/models/assignment_spec.rb
+++ b/spec/models/assignment_spec.rb
@@ -1960,20 +1960,20 @@ describe Assignment do
       assignment.turnitin_settings = {
         :originality_report_visibility => 'invalid',
         :s_paper_check => '2',
-        :internet_check => '2',
-        :journal_check => '2',
-        :exclude_biblio => '2',
-        :exclude_quoted => '2',
+        :internet_check => 1,
+        :journal_check => 0,
+        :exclude_biblio => true,
+        :exclude_quoted => false,
         :exclude_type => '3',
         :exclude_value => 'asdf',
         :bogus => 'haha'
       }
       assignment.turnitin_settings.should eql({
         :originality_report_visibility => 'immediate',
-        :s_paper_check => '0',
-        :internet_check => '0',
+        :s_paper_check => '1',
+        :internet_check => '1',
         :journal_check => '0',
-        :exclude_biblio => '0',
+        :exclude_biblio => '1',
         :exclude_quoted => '0',
         :exclude_type => '0',
         :exclude_value => ''