diff --git a/cms/static/cms/js/require-config.js b/cms/static/cms/js/require-config.js
index 4e5be98dfc..8139da6206 100644
--- a/cms/static/cms/js/require-config.js
+++ b/cms/static/cms/js/require-config.js
@@ -1,3 +1,16 @@
+if (window) {
+    // MathJax Fast Preview was introduced in 2.5. However, it
+    // causes undesirable flashing/font size changes when
+    // MathJax is used for interactive preview (equation editor).
+    // Setting processSectionDelay to 0 (see below) fully eliminates
+    // fast preview, but to reduce confusion, we are also setting
+    // the option as displayed in the context menu to false.
+    // When upgrading to 2.6, check if this variable name changed.
+    window.MathJax = {
+      menuSettings: {CHTMLpreview: false}
+    };
+}
+
 require.config({
     // NOTE: baseUrl has been previously set in cms/static/templates/base.html
     waitSeconds: 60,
@@ -70,7 +83,7 @@ require.config({
         // end of Annotation tool files
 
         // externally hosted files
-        "mathjax": "//cdn.mathjax.org/mathjax/2.4-latest/MathJax.js?config=TeX-MML-AM_HTMLorMML-full&delayStartupUntil=configured",
+        "mathjax": "//cdn.mathjax.org/mathjax/2.5-latest/MathJax.js?config=TeX-MML-AM_HTMLorMML-full&delayStartupUntil=configured",
         "youtube": [
             // youtube URL does not end in ".js". We add "?noext" to the path so
             // that require.js adds the ".js" to the query component of the URL,
@@ -191,6 +204,12 @@ require.config({
                   ]
                 }
               });
+              // In order to eliminate all flashing during interactive
+              // preview, it is necessary to set processSectionDelay to 0
+              // (remove delay between input and output phases). This
+              // effectively disables fast preview, regardless of
+              // the fast preview setting as shown in the context menu.
+              MathJax.Hub.processSectionDelay = 0;
               MathJax.Hub.Configured();
             }
         },
diff --git a/cms/static/coffee/spec/main.coffee b/cms/static/coffee/spec/main.coffee
index 14315b5236..a2a5cb3083 100644
--- a/cms/static/coffee/spec/main.coffee
+++ b/cms/static/coffee/spec/main.coffee
@@ -51,7 +51,7 @@ requirejs.config({
         "URI": "xmodule_js/common_static/js/vendor/URI.min",
         "mock-ajax": "xmodule_js/common_static/js/vendor/mock-ajax",
 
-        "mathjax": "//cdn.mathjax.org/mathjax/2.4-latest/MathJax.js?config=TeX-MML-AM_HTMLorMML-full&delayStartupUntil=configured",
+        "mathjax": "//cdn.mathjax.org/mathjax/2.5-latest/MathJax.js?config=TeX-MML-AM_HTMLorMML-full&delayStartupUntil=configured",
         "youtube": "//www.youtube.com/player_api?noext",
 
         "coffee/src/ajax_prefix": "xmodule_js/common_static/coffee/src/ajax_prefix",
diff --git a/cms/static/coffee/spec/main_squire.coffee b/cms/static/coffee/spec/main_squire.coffee
index f9053e5e3b..20cb7bc7a0 100644
--- a/cms/static/coffee/spec/main_squire.coffee
+++ b/cms/static/coffee/spec/main_squire.coffee
@@ -42,7 +42,7 @@ requirejs.config({
         "domReady": "xmodule_js/common_static/js/vendor/domReady",
         "URI": "xmodule_js/common_static/js/vendor/URI.min",
 
-        "mathjax": "//cdn.mathjax.org/mathjax/2.4-latest/MathJax.js?config=TeX-MML-AM_HTMLorMML-full&delayStartupUntil=configured",
+        "mathjax": "//cdn.mathjax.org/mathjax/2.5-latest/MathJax.js?config=TeX-MML-AM_HTMLorMML-full&delayStartupUntil=configured",
         "youtube": "//www.youtube.com/player_api?noext",
 
         "coffee/src/ajax_prefix": "xmodule_js/common_static/coffee/src/ajax_prefix"
diff --git a/common/static/js/capa/spec/formula_equation_preview_spec.js b/common/static/js/capa/spec/formula_equation_preview_spec.js
index fe97d8fbc8..0bf4ffacb8 100644
--- a/common/static/js/capa/spec/formula_equation_preview_spec.js
+++ b/common/static/js/capa/spec/formula_equation_preview_spec.js
@@ -235,8 +235,7 @@ describe("Formula Equation Preview", function () {
 
                 // Refresh the MathJax.
                 expect(MathJax.Hub.Queue).toHaveBeenCalledWith(
-                    ['Text', this.jax, 'THE_FORMULA'],
-                    ['Reprocess', this.jax]
+                    ['Text', this.jax, 'THE_FORMULA']
                 );
             });
         });
@@ -302,8 +301,7 @@ describe("Formula Equation Preview", function () {
             runs(function () {
                 // Refresh the MathJax.
                 expect(MathJax.Hub.Queue).toHaveBeenCalledWith(
-                    ['Text', this.jax, '\\text{OOPSIE}'],
-                    ['Reprocess', this.jax]
+                    ['Text', this.jax, '\\text{OOPSIE}']
                 );
                 expect($img.css('visibility')).toEqual('hidden');
             });
@@ -349,17 +347,15 @@ describe("Formula Equation Preview", function () {
 
             this.callbacks[0](this.responses[0]);
             expect(MathJax.Hub.Queue).toHaveBeenCalledWith(
-                ['Text', this.jax, 'THE_FORMULA_0'],
-                ['Reprocess', this.jax]
+                ['Text', this.jax, 'THE_FORMULA_0']
             );
             expect($img.css('visibility')).toEqual('visible');
 
             this.callbacks[1](this.responses[1]);
             expect(MathJax.Hub.Queue).toHaveBeenCalledWith(
-                ['Text', this.jax, 'THE_FORMULA_1'],
-                ['Reprocess', this.jax]
+                ['Text', this.jax, 'THE_FORMULA_1']
             );
-            expect($img.css('visibility')).toEqual('hidden')
+            expect($img.css('visibility')).toEqual('hidden');
         });
 
         it("doesn't display outdated information", function () {
@@ -370,15 +366,14 @@ describe("Formula Equation Preview", function () {
             // Switch the order (1 returns before 0)
             this.callbacks[1](this.responses[1]);
             expect(MathJax.Hub.Queue).toHaveBeenCalledWith(
-                ['Text', this.jax, 'THE_FORMULA_1'],
-                ['Reprocess', this.jax]
+                ['Text', this.jax, 'THE_FORMULA_1']
             );
-            expect($img.css('visibility')).toEqual('hidden')
+            expect($img.css('visibility')).toEqual('hidden');
 
             MathJax.Hub.Queue.reset();
             this.callbacks[0](this.responses[0]);
             expect(MathJax.Hub.Queue).not.toHaveBeenCalled();
-            expect($img.css('visibility')).toEqual('hidden')
+            expect($img.css('visibility')).toEqual('hidden');
         });
 
         it("doesn't show an error if the responses are close together",
@@ -392,8 +387,7 @@ describe("Formula Equation Preview", function () {
 
                this.callbacks[1](this.responses[1]);
                expect(MathJax.Hub.Queue).toHaveBeenCalledWith(
-                   ['Text', this.jax, 'THE_FORMULA_1'],
-                   ['Reprocess', this.jax]
+                   ['Text', this.jax, 'THE_FORMULA_1']
                );
 
                // Make sure that it doesn't indeed show up later
diff --git a/common/static/js/capa/src/formula_equation_preview.js b/common/static/js/capa/src/formula_equation_preview.js
index 9930d99364..3c01cab909 100644
--- a/common/static/js/capa/src/formula_equation_preview.js
+++ b/common/static/js/capa/src/formula_equation_preview.js
@@ -139,8 +139,7 @@ formulaEquationPreview.enable = function () {
                         if (inputData.jax) {
                             // Set the text as the latex code, and then update the MathJax.
                             MathJax.Hub.Queue(
-                                ['Text', inputData.jax, latex],
-                                ['Reprocess', inputData.jax]
+                                ['Text', inputData.jax, latex]
                             );
                         } else if (latex) {
                             console.log("[FormulaEquationInput] Oops no mathjax for ", latex);
diff --git a/common/templates/mathjax_include.html b/common/templates/mathjax_include.html
index f15fc0fc67..a57ef69e13 100644
--- a/common/templates/mathjax_include.html
+++ b/common/templates/mathjax_include.html
@@ -1,11 +1,28 @@
 ## mako
 ## File:   templates/mathjax_include.html
 ##
-## Advanced mathjax using 2.0-latest CDN for Dynamic Math
-##
-## This enables ASCIIMathJAX, and is used by js_textbox
+## Note that this file is only used by LMS.
+## MathJax configuration for Studio lives in
+## cms/js/require-config.js.
 
 
+<%page args="disable_fast_preview=True"/>
+
+%if disable_fast_preview:
+// Fast Preview was introduced in 2.5. However, it
+// causes undesirable flashing/font size changes when
+// MathJax is used for interactive preview (equation editor).
+// Setting processSectionDelay to 0 (see below) fully eliminates
+// fast preview, but to reduce confusion, we are also setting
+// the option as displayed in the context menu to false.
+// When upgrading to 2.6, check if this variable name changed.
+<script type="text/javascript">
+    window.MathJax = {
+      menuSettings: {CHTMLpreview: false}
+    };
+</script>
+%endif
+
 %if mathjax_mode is not Undefined and mathjax_mode == 'wiki':
 <script type="text/x-mathjax-config">
   MathJax.Hub.Config({
@@ -30,7 +47,16 @@
 </script>
 %endif
 <script type="text/x-mathjax-config">
-  window.HUB = MathJax.Hub;
+
+  %if disable_fast_preview:
+  // In order to eliminate all flashing during interactive
+  // preview, it is necessary to set processSectionDelay to 0
+  // (remove delay between input and output phases). This
+  // effectively disables fast preview, regardless of
+  // the fast preview setting as shown in the context menu.
+  MathJax.Hub.processSectionDelay = 0;
+  %endif
+
   MathJax.Hub.signal.Interest(function(message) {
     if(message[0] === "End Math") {
         set_mathjax_display_div_settings();
@@ -50,4 +76,4 @@
 <!-- This must appear after all mathjax-config blocks, so it is after the imports from the other templates.
      It can't be run through static.url because MathJax uses crazy url introspection to do lazy loading of
      MathJax extension libraries -->
-<script type="text/javascript" src="https://cdn.mathjax.org/mathjax/2.4-latest/MathJax.js?config=TeX-MML-AM_HTMLorMML-full"></script>
+<script type="text/javascript" src="https://cdn.mathjax.org/mathjax/2.5-latest/MathJax.js?config=TeX-MML-AM_HTMLorMML-full"></script>
diff --git a/lms/static/js/spec/main.js b/lms/static/js/spec/main.js
index a7d585ad11..fef5af93a9 100644
--- a/lms/static/js/spec/main.js
+++ b/lms/static/js/spec/main.js
@@ -49,7 +49,7 @@
             'jasmine.async': 'xmodule_js/common_static/js/vendor/jasmine.async',
             'draggabilly': 'xmodule_js/common_static/js/vendor/draggabilly.pkgd',
             'domReady': 'xmodule_js/common_static/js/vendor/domReady',
-            'mathjax': '//cdn.mathjax.org/mathjax/2.4-latest/MathJax.js?config=TeX-MML-AM_HTMLorMML-full&delayStartupUntil=configured', // jshint ignore:line
+            'mathjax': '//cdn.mathjax.org/mathjax/2.5-latest/MathJax.js?config=TeX-MML-AM_HTMLorMML-full&delayStartupUntil=configured', // jshint ignore:line
             'youtube': '//www.youtube.com/player_api?noext',
             'coffee/src/ajax_prefix': 'xmodule_js/common_static/coffee/src/ajax_prefix',
             'coffee/src/instructor_dashboard/student_admin': 'coffee/src/instructor_dashboard/student_admin',
diff --git a/lms/templates/discussion/_js_body_dependencies.html b/lms/templates/discussion/_js_body_dependencies.html
index 801e275ebf..447af19652 100644
--- a/lms/templates/discussion/_js_body_dependencies.html
+++ b/lms/templates/discussion/_js_body_dependencies.html
@@ -1 +1,3 @@
-<%include file="/mathjax_include.html" />
+<%page args="disable_fast_preview=True"/>
+
+<%include file="/mathjax_include.html" args="disable_fast_preview=disable_fast_preview"/>
diff --git a/lms/templates/discussion/index.html b/lms/templates/discussion/index.html
index 3363f6ac83..3be7b41ab3 100644
--- a/lms/templates/discussion/index.html
+++ b/lms/templates/discussion/index.html
@@ -18,7 +18,8 @@ from django.core.urlresolvers import reverse
 </%block>
 
 <%block name="js_extra">
-<%include file="_js_body_dependencies.html" />
+## Enable fast preview to fix discussion MathJax rendering bug when page first loads.
+<%include file="_js_body_dependencies.html" args="disable_fast_preview=False"/>
 <%static:js group='discussion'/>
 </%block>