diff --git a/lib/outputcomponents.php b/lib/outputcomponents.php
index 09eb0bdac1f..0621e914c8f 100644
--- a/lib/outputcomponents.php
+++ b/lib/outputcomponents.php
@@ -1680,7 +1680,7 @@ class html_writer {
             $class = str_replace(']', '', $class);
             $attributes['class'] = $class;
         }
-        $attributes['class'] = 'select ' . $attributes['class']; // Add 'select' selector always
+        $attributes['class'] = 'select custom-select ' . $attributes['class']; // Add 'select' selector always
 
         $attributes['name'] = $name;
 
diff --git a/report/log/classes/renderer.php b/report/log/classes/renderer.php
index dc7cbea2cc0..9003b59de24 100644
--- a/report/log/classes/renderer.php
+++ b/report/log/classes/renderer.php
@@ -186,7 +186,8 @@ class report_log_renderer extends plugin_renderer_base {
                         array('class' => 'accesshide'));
                 echo html_writer::select($readers, 'logreader', $reportlog->selectedlogreader, false);
             }
-            echo html_writer::empty_tag('input', array('type' => 'submit', 'value' => get_string('gettheselogs')));
+            echo html_writer::empty_tag('input', array('type' => 'submit', 'value' => get_string('gettheselogs'),
+                'class' => 'btn btn-primary'));
         }
         echo html_writer::end_div();
         echo html_writer::end_tag('form');
diff --git a/report/loglive/classes/renderer.php b/report/loglive/classes/renderer.php
index c65e78e72cf..e92a2473aa5 100644
--- a/report/loglive/classes/renderer.php
+++ b/report/loglive/classes/renderer.php
@@ -90,7 +90,8 @@ class report_loglive_renderer extends plugin_renderer_base {
     public function toggle_liveupdate_button(report_loglive_renderable $reportloglive) {
         // Add live log controls.
         if ($reportloglive->page == 0 && $reportloglive->selectedlogreader) {
-            echo html_writer::tag('button' , get_string('pause', 'report_loglive'), array('id' => 'livelogs-pause-button'));
+            echo html_writer::tag('button' , get_string('pause', 'report_loglive'),
+                array('id' => 'livelogs-pause-button', 'class' => 'btn btn-secondary'));
             $icon = new pix_icon('i/loading_small', 'loading', 'moodle', array('class' => 'spinner'));
             return html_writer::tag('span', $this->output->render($icon), array('class' => 'spinner'));
         }
diff --git a/report/participation/index.php b/report/participation/index.php
index 77f75957b0f..964a1690c03 100644
--- a/report/participation/index.php
+++ b/report/participation/index.php
@@ -370,19 +370,20 @@ if (!empty($instanceid) && !empty($roleid)) {
     }
 
     if (!empty($CFG->messaging)) {
-        echo '<div class="selectbuttons">';
-        echo '<input type="button" id="checkall" value="'.get_string('selectall').'" /> '."\n";
-        echo '<input type="button" id="checknone" value="'.get_string('deselectall').'" /> '."\n";
+        $buttonclasses = 'btn btn-secondary';
+        echo '<div class="selectbuttons btn-group">';
+        echo '<input type="button" id="checkall" value="'.get_string('selectall').'" class="'. $buttonclasses .'"> '."\n";
+        echo '<input type="button" id="checknone" value="'.get_string('deselectall').'" class="'. $buttonclasses .'"> '."\n";
         if ($perpage >= $matchcount) {
-            echo '<input type="button" id="checknos" value="'.get_string('selectnos').'" />'."\n";
+            echo '<input type="button" id="checknos" value="'.get_string('selectnos').'" class="'. $buttonclasses .'">'."\n";
         }
         echo '</div>';
-        echo '<div>';
+        echo '<div class="p-y-1">';
         echo html_writer::label(get_string('withselectedusers'), 'formactionselect');
         $displaylist['messageselect.php'] = get_string('messageselectadd');
         echo html_writer::select($displaylist, 'formaction', '', array('' => 'choosedots'), array('id' => 'formactionselect'));
         echo $OUTPUT->help_icon('withselectedusers');
-        echo '<input type="submit" value="' . get_string('ok') . '" />'."\n";
+        echo '<input type="submit" value="' . get_string('ok') . '" class="'. $buttonclasses .'"/>'."\n";
         echo '</div>';
         echo '</div>'."\n";
         echo '</form>'."\n";
diff --git a/report/participation/locallib.php b/report/participation/locallib.php
index 49bbfe5f0e8..7fb1206d672 100644
--- a/report/participation/locallib.php
+++ b/report/participation/locallib.php
@@ -222,13 +222,23 @@ function report_participation_print_filter_form($course, $timefrom, $minlog, $ac
 
     echo '<form class="participationselectform" action="index.php" method="get"><div>'."\n".
         '<input type="hidden" name="id" value="'.$course->id.'" />'."\n";
+    echo '<div class="form-group">'."\n";
     echo '<label for="menuinstanceid">'.get_string('activitymodule').'</label>'."\n";
     echo html_writer::select($instanceoptions, 'instanceid', $instanceid);
+    echo '</div>'."\n";
+    echo '<div class="form-group form-inline">'."\n";
+    echo '<div class="form-group">'."\n";
     echo '<label for="menutimefrom">'.get_string('lookback').'</label>'."\n";
     echo html_writer::select($timeoptions,'timefrom',$timefrom);
+    echo '</div>'."\n";
+    echo '<div class="form-group">'."\n";
     echo '<label for="menuroleid">'.get_string('showonly').'</label>'."\n";
     echo html_writer::select($roleoptions,'roleid',$roleid,false);
+    echo '</div>'."\n";
+    echo '<div class="form-group">'."\n";
     echo '<label for="menuaction">'.get_string('showactions').'</label>'."\n";
     echo html_writer::select($actionoptions,'action',$action,false);
-    echo '<input type="submit" value="'.get_string('go').'" />'."\n</div></form>\n";
+    echo '</div>'."\n";
+    echo '</div>'."\n";
+    echo '<input type="submit" value="'.get_string('go').'" class="btn btn-primary" />'."\n</div></form>\n";
 }