diff --git a/packages/processor/README.md b/packages/processor/README.md
index aafc83043..30b7634f7 100644
--- a/packages/processor/README.md
+++ b/packages/processor/README.md
@@ -56,6 +56,11 @@ Returns a promise. Add `file` to the `Processor` instance with `css` contents.
 
 Returns a promise. Add `file` to the `Processor` instance, reads contents from disk using `fs`.
 
+### `.root(file, Root)`
+
+Returns a promise. Add `file` to the `Processor` instance, re-uses a Postcss `Root` object, avoiding
+unnecessarily parsing an AST again.
+
 ### `.output({ args })`
 
 Returns a promise. Finalize processing of all added CSS and create combined CSS output file.
diff --git a/packages/processor/processor.js b/packages/processor/processor.js
index 395be58b0..3fddc0b6f 100644
--- a/packages/processor/processor.js
+++ b/packages/processor/processor.js
@@ -41,7 +41,7 @@ class Processor {
             {
                 cwd : process.cwd(),
                 map : false,
-                
+
                 dupewarn     : true,
                 exportValues : true,
                 loadFile     : defaultLoadFile,
@@ -123,7 +123,7 @@ class Processor {
         this._log("file()", id);
 
         const text = await this._loadFile(id);
-        
+
         return this._add(id, text);
     }
 
@@ -136,6 +136,15 @@ class Processor {
         return this._add(id, text);
     }
 
+    // Add an existing postcss Root object by name
+    root(file, root) {
+        const id = this._normalize(file);
+
+        this._log("root()", id);
+
+        return this._add(id, root);
+    }
+
     // Remove a file from the dependency graph
     remove(input) {
         // Only want files actually in the array
@@ -351,7 +360,7 @@ class Processor {
 
     // Take a file id and some text, walk it for dependencies, then
     // process and return details
-    async _add(id, text) {
+    async _add(id, src) {
         const check = id.toLowerCase();
 
         // Warn about potential dupes if an ID goes past we've seen before
@@ -368,7 +377,7 @@ class Processor {
 
         this._log("_add()", id);
 
-        await this._walk(id, text);
+        await this._walk(id, src);
 
         const deps = [ ...this._graph.dependenciesOf(id), id ];
 
@@ -424,7 +433,7 @@ class Processor {
 
     // Process files and walk their composition/value dependency tree to find
     // new files we need to process
-    async _walk(name, text) {
+    async _walk(name, src) {
         // No need to re-process files unless they've been marked invalid
         if(this._files[name] && this._files[name].valid) {
             // Do want to wait until they're done being processed though
@@ -440,12 +449,12 @@ class Processor {
         let walked;
 
         const file = this._files[name] = {
-            text,
+            text    : typeof src === "string" ? src : src.source.input.css,
             exports : false,
             values  : false,
             valid   : true,
             before  : this._before.process(
-                text,
+                src,
                 params(this, {
                     from : name,
                 })
@@ -471,7 +480,7 @@ class Processor {
         await Promise.all(
             this._graph.dependenciesOf(name).map((dependency) => {
                 const { valid, walked : complete } = this._files[dependency] || false;
-                
+
                 // If the file hasn't been invalidated wait for it to be done processing
                 if(valid) {
                     return complete;
diff --git a/packages/processor/test/__snapshots__/api.test.js.snap b/packages/processor/test/__snapshots__/api.test.js.snap
index d46b0e4a3..c93a4f79b 100644
--- a/packages/processor/test/__snapshots__/api.test.js.snap
+++ b/packages/processor/test/__snapshots__/api.test.js.snap
@@ -1,17 +1,5 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`/processor.js API .resolve() should fall back to a default resolver 1`] = `
-Array [
-  "packages/processor/test/specimens/local.css",
-]
-`;
-
-exports[`/processor.js API .resolve() should run resolvers until a match is found 1`] = `
-Array [
-  "packages/processor/test/specimens/local.css",
-]
-`;
-
 exports[`/processor.js API .compositions should return compositions for loaded files 1`] = `Promise {}`;
 
 exports[`/processor.js API .dependencies() should return the dependencies of the specified file 1`] = `
@@ -310,6 +298,38 @@ Array [
 ]
 `;
 
+exports[`/processor.js API .resolve() should fall back to a default resolver 1`] = `
+Array [
+  "packages/processor/test/specimens/local.css",
+]
+`;
+
+exports[`/processor.js API .resolve() should run resolvers until a match is found 1`] = `
+Array [
+  "packages/processor/test/specimens/local.css",
+]
+`;
+
+exports[`/processor.js API .root() should process a postcss Root 1`] = `
+Object {
+  "wooga": Array [
+    "wooga",
+  ],
+}
+`;
+
+exports[`/processor.js API .root() should process a postcss Root 2`] = `
+Object {
+  "wooga": Array [
+    "wooga",
+  ],
+}
+`;
+
+exports[`/processor.js API .root() should process a postcss Root 3`] = `".wooga { }"`;
+
+exports[`/processor.js API .root() should process a postcss Root 4`] = `".wooga { }"`;
+
 exports[`/processor.js API .string() should process a string 1`] = `
 Object {
   "wooga": Array [
diff --git a/packages/processor/test/api.test.js b/packages/processor/test/api.test.js
index 3dd126386..db25f290b 100644
--- a/packages/processor/test/api.test.js
+++ b/packages/processor/test/api.test.js
@@ -1,5 +1,6 @@
 "use strict";
 
+const postcss  = require("postcss");
 const namer    = require("@modular-css/test-utils/namer.js");
 const relative = require("@modular-css/test-utils/relative.js");
 
@@ -19,6 +20,21 @@ describe("/processor.js", () => {
             expect(typeof Processor).toBe("function");
         });
 
+        describe(".root()", () => {
+            it("should process a postcss Root", async () => {
+                const file = "./simple.css";
+                const root = postcss.parse(".wooga { }", { from : file });
+                const result = await processor.root(
+                    file, root
+                );
+
+                expect(result.exports).toMatchSnapshot();
+                expect(result.details.exports).toMatchSnapshot();
+                expect(result.details.text).toMatchSnapshot();
+                expect(result.details.processed.root.toResult().css).toMatchSnapshot();
+            });
+        });
+
         describe(".string()", () => {
             it("should process a string", async () => {
                 const result = await processor.string(