diff --git a/src/execution/collectFields.ts b/src/execution/collectFields.ts
index 06ade32c5b..03d163373f 100644
--- a/src/execution/collectFields.ts
+++ b/src/execution/collectFields.ts
@@ -21,8 +21,8 @@ import { typeFromAST } from '../utilities/typeFromAST';
 
 import { getDirectiveValues } from './values';
 
-interface FragmentEntry {
-  fragment: FragmentDefinitionNode;
+interface StackEntry {
+  selectionSet: SelectionSetNode;
   runtimeType: GraphQLObjectType;
 }
 
@@ -42,31 +42,21 @@ export function collectFields(
   runtimeType: GraphQLObjectType,
   selectionSet: SelectionSetNode,
 ): Map<string, ReadonlyArray<FieldNode>> {
-  const foundFragments: Array<FragmentEntry> = [];
+  const stack: Array<StackEntry> = [{ selectionSet, runtimeType }];
   const fields = new Map();
   const visited = new Set<string>();
-  collectFieldsImpl(
-    schema,
-    fragments,
-    variableValues,
-    runtimeType,
-    selectionSet,
-    fields,
-    visited,
-    foundFragments,
-  );
 
   let entry;
-  while ((entry = foundFragments.pop()) !== undefined) {
+  while ((entry = stack.shift()) !== undefined) {
     collectFieldsImpl(
       schema,
       fragments,
       variableValues,
       entry.runtimeType,
-      entry.fragment.selectionSet,
+      entry.selectionSet,
       fields,
       visited,
-      foundFragments,
+      stack,
     );
   }
 
@@ -91,34 +81,25 @@ export function collectSubfields(
   fieldNodes: ReadonlyArray<FieldNode>,
 ): Map<string, ReadonlyArray<FieldNode>> {
   const subFieldNodes = new Map();
-  const foundFragments: Array<FragmentEntry> = [];
+  const stack: Array<StackEntry> = [];
   const visitedFragmentNames = new Set<string>();
   for (const node of fieldNodes) {
     if (node.selectionSet) {
-      collectFieldsImpl(
-        schema,
-        fragments,
-        variableValues,
-        returnType,
-        node.selectionSet,
-        subFieldNodes,
-        visitedFragmentNames,
-        foundFragments,
-      );
+      stack.push({ selectionSet: node.selectionSet, runtimeType: returnType });
     }
   }
 
   let entry;
-  while ((entry = foundFragments.pop()) !== undefined) {
+  while ((entry = stack.shift()) !== undefined) {
     collectFieldsImpl(
       schema,
       fragments,
       variableValues,
       entry.runtimeType,
-      entry.fragment.selectionSet,
+      entry.selectionSet,
       subFieldNodes,
       visitedFragmentNames,
-      foundFragments,
+      stack,
     );
   }
 
@@ -133,8 +114,9 @@ function collectFieldsImpl(
   selectionSet: SelectionSetNode,
   fields: Map<string, Array<FieldNode>>,
   visitedFragmentNames: Set<string>,
-  foundFragments: Array<FragmentEntry>,
+  stack: Array<StackEntry>,
 ): void {
+  const discovered = [];
   for (const selection of selectionSet.selections) {
     switch (selection.kind) {
       case Kind.FIELD: {
@@ -157,16 +139,7 @@ function collectFieldsImpl(
         ) {
           continue;
         }
-        collectFieldsImpl(
-          schema,
-          fragments,
-          variableValues,
-          runtimeType,
-          selection.selectionSet,
-          fields,
-          visitedFragmentNames,
-          foundFragments,
-        );
+        discovered.push({ selectionSet: selection.selectionSet, runtimeType });
         break;
       }
       case Kind.FRAGMENT_SPREAD: {
@@ -186,11 +159,15 @@ function collectFieldsImpl(
           continue;
         }
 
-        foundFragments.push({ runtimeType, fragment });
+        discovered.push({ selectionSet: fragment.selectionSet, runtimeType });
         break;
       }
     }
   }
+
+  if (discovered.length !== 0) {
+    stack.unshift(...discovered);
+  }
 }
 
 /**