diff --git a/.eslintrc b/.eslintrc
index 0d67347a..aacaef35 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -8,7 +8,7 @@
         "max-len": [2, 80, 4],
         "semi": [2, "always"],
         "strict": [2, "never"],
-        "no-console": [2, {"allow": ["log", "warn", "error"]}]
+        "no-console": [2, {"allow": ["log", "warn", "error", "groupCollapsed", "groupEnd"]}]
     },
     "env": {
         "node": true,
diff --git a/src/blocks/scratch3.js b/src/blocks/scratch3.js
index 6bf32764..a2f13253 100644
--- a/src/blocks/scratch3.js
+++ b/src/blocks/scratch3.js
@@ -23,7 +23,6 @@ Scratch3Blocks.prototype.getPrimitives = function() {
 };
 
 Scratch3Blocks.prototype.repeat = function(argValues, util) {
-    console.log('Running: control_repeat');
     // Initialize loop
     if (util.stackFrame.loopCounter === undefined) {
         util.stackFrame.loopCounter = parseInt(argValues[0]); // @todo arg
@@ -37,12 +36,10 @@ Scratch3Blocks.prototype.repeat = function(argValues, util) {
 };
 
 Scratch3Blocks.prototype.forever = function(argValues, util) {
-    console.log('Running: control_forever');
     util.startSubstack();
 };
 
 Scratch3Blocks.prototype.wait = function(argValues, util) {
-    console.log('Running: control_wait');
     util.yield();
     util.timeout(function() {
         util.done();
@@ -50,23 +47,19 @@ Scratch3Blocks.prototype.wait = function(argValues, util) {
 };
 
 Scratch3Blocks.prototype.stop = function() {
-    console.log('Running: control_stop');
     // @todo - don't use this.runtime
     this.runtime.stopAll();
 };
 
 Scratch3Blocks.prototype.whenFlagClicked = function() {
-    console.log('Running: event_whenflagclicked');
     // No-op
 };
 
 Scratch3Blocks.prototype.whenBroadcastReceived = function() {
-    console.log('Running: event_whenbroadcastreceived');
     // No-op
 };
 
 Scratch3Blocks.prototype.broadcast = function(argValues, util) {
-    console.log('Running: event_broadcast');
     util.startHats(function(hat) {
         if (hat.opcode === 'event_whenbroadcastreceived') {
             var shadows = hat.fields.CHOICE.blocks;
diff --git a/src/blocks/wedo2.js b/src/blocks/wedo2.js
index 86c73de0..5074b26a 100644
--- a/src/blocks/wedo2.js
+++ b/src/blocks/wedo2.js
@@ -144,11 +144,9 @@ WeDo2Blocks.prototype.setColor = function(argValues, util) {
 };
 
 WeDo2Blocks.prototype.whenDistanceClose = function() {
-    console.log('Running: wedo_whendistanceclose');
 };
 
 WeDo2Blocks.prototype.whenTilt = function() {
-    console.log('Running: wedo_whentilt');
 };
 
 module.exports = WeDo2Blocks;
diff --git a/src/engine/sequencer.js b/src/engine/sequencer.js
index 2f1126d4..a1572c3b 100644
--- a/src/engine/sequencer.js
+++ b/src/engine/sequencer.js
@@ -24,6 +24,12 @@ function Sequencer (runtime) {
  */
 Sequencer.WORK_TIME = 10;
 
+/**
+ * If set, block calls, args, and return values will be logged to the console.
+ * @const {boolean}
+ */
+Sequencer.DEBUG_BLOCK_CALLS = true;
+
 /**
  * Step through all threads in `this.threads`, running them in order.
  * @return {Array.<Thread>} All threads which have finished in this iteration.
@@ -213,9 +219,15 @@ Sequencer.prototype.stepThread = function (thread) {
             console.warn('Could not get implementation for opcode: ' + opcode);
         }
         else {
+            if (Sequencer.DEBUG_BLOCK_CALLS) {
+                console.groupCollapsed('Executing: ' + opcode);
+                console.log('with arguments: ', argValues);
+                console.log('and stack frame: ', currentStackFrame);
+            }
+            var blockFunctionReturnValue = null;
             try {
                 // @todo deal with the return value
-                blockFunction(argValues, {
+                blockFunctionReturnValue = blockFunction(argValues, {
                     yield: threadYieldCallback,
                     done: threadDoneCallback,
                     timeout: YieldTimers.timeout,
@@ -238,6 +250,11 @@ Sequencer.prototype.stepThread = function (thread) {
                     // Thread executed without yielding - move to done
                     threadDoneCallback();
                 }
+                if (Sequencer.DEBUG_BLOCK_CALLS) {
+                    console.log('ending stack frame: ', currentStackFrame);
+                    console.log('returned: ', blockFunctionReturnValue);
+                    console.groupEnd();
+                }
             }
         }
     }