diff --git a/T4.Build/.gitignore b/T4.Build/.gitignore
new file mode 100644
index 0000000..eeaa096
--- /dev/null
+++ b/T4.Build/.gitignore
@@ -0,0 +1,2 @@
+# Ignore any immediate `tools` directories, as they are likely someone building and testing locally from another project
+/tools/*
\ No newline at end of file
diff --git a/T4.Build/BuildTemplateGenerator.cs b/T4.Build/BuildTemplateGenerator.cs
index a117e62..f867942 100644
--- a/T4.Build/BuildTemplateGenerator.cs
+++ b/T4.Build/BuildTemplateGenerator.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.CodeDom.Compiler;
 using System.IO;
+using System.Text;
 using Mono.TextTemplating;
 
 namespace T4.Build
@@ -11,6 +12,7 @@ class BuildTemplateGenerator : TemplateGenerator
         List<string> includedFiles = new List<string>();
         string lockPath;
         ParsedTemplate parsedTemplate;
+        readonly Func<string, string> preprocessor = null;
 
         public BuildTemplateGenerator(string template)
         {
@@ -18,6 +20,12 @@ public BuildTemplateGenerator(string template)
             Engine.UseInProcessCompiler();
         }
 
+        public BuildTemplateGenerator(string template, Func<string, string> preprocessor)
+            : this(template)
+        {
+            this.preprocessor = preprocessor;
+        }
+
         public string[] IncludedFiles
         {
             get
@@ -98,24 +106,64 @@ public bool ProcessTemplate(bool skipUpToDate, out bool skipped)
         {
             skipped = false;
 
-            if (string.IsNullOrEmpty(OutputFile))
+            var outputFile = OutputFile;
+            if (string.IsNullOrWhiteSpace(outputFile))
+            {
                 return false;
+            }
 
             if (skipUpToDate)
             {
                 var templateInfo = new FileInfo(TemplateFile);
-                var outputInfo = new FileInfo(OutputFile);
+                var outputInfo = new FileInfo(outputFile);
                 if (outputInfo.Exists
-                && templateInfo.LastWriteTime.Ticks < outputInfo.LastWriteTime.Ticks
-&& includedFiles.TrueForAll(x => (new FileInfo(x)).LastWriteTime.Ticks < outputInfo.LastWriteTime.Ticks)
+                    && templateInfo.LastWriteTime.Ticks < outputInfo.LastWriteTime.Ticks
+                    && includedFiles.TrueForAll(x => (new FileInfo(x)).LastWriteTime.Ticks < outputInfo.LastWriteTime.Ticks)
                 )
                 {
                     skipped = true;
                     return true;
                 }
             }
-            return ProcessTemplate(TemplateFile, OutputFile);
+
+            string content;
+            try
+            {
+                content = File.ReadAllText(TemplateFile);
+            }
+            catch (IOException ex)
+            {
+                Errors.Clear();
+                AddError($"Could not read input file '{TemplateFile}':\n{ex}");
+                return false;
+            }
+
+            if (!(preprocessor is null))
+            {
+                content = preprocessor(content);
+            }
+            ProcessTemplate(TemplateFile, content, ref outputFile, out var output);
+
+            try
+            {
+                if (!Errors.HasErrors)
+                {
+                    File.WriteAllText(outputFile, output, new UTF8Encoding(encoderShouldEmitUTF8Identifier: false));
+                }
+            }
+            catch (IOException ex)
+            {
+                AddError($"Could not write output file '{outputFile}':\n{ex}");
+            }
+
+            return !Errors.HasErrors;
         }
 
+        CompilerError AddError(string error)
+        {
+            var err = new CompilerError { ErrorText = error };
+            Errors.Add(err);
+            return err;
+        }
     }
 }
\ No newline at end of file
diff --git a/T4.Build/Program.cs b/T4.Build/Program.cs
index 725cbcf..67a42f0 100644
--- a/T4.Build/Program.cs
+++ b/T4.Build/Program.cs
@@ -2,6 +2,7 @@
 using System.CodeDom.Compiler;
 using System.Collections;
 using System.Collections.Concurrent;
+using System.Collections.Generic;
 using System.CommandLine;
 using System.CommandLine.Invocation;
 using System.Diagnostics;
@@ -30,7 +31,12 @@ static int Main(string[] args)
             transformCommand.Add(skipOption);
             var parallelOption = new Option<bool>(new[] { "--parallel", "-p" }, "Transform templates in parallel");
             transformCommand.Add(parallelOption);
-            transformCommand.Handler = CommandHandler.Create<FileInfo[], int, bool, bool>(Transform);
+            var variableOptions = new Option<string[]>(new[] { "--variable", "-v" }, "T4ParameterValues variable to replace within the template; syntax is \"Include=Value\"")
+            {
+                AllowMultipleArgumentsPerToken = false,
+            };
+            transformCommand.Add(variableOptions);
+            transformCommand.Handler = CommandHandler.Create<FileInfo[], int, bool, bool, string[]>(Transform);
             rootCommand.Add(transformCommand);
 
             var cleanCommand = new Command("clean", "List the output files");
@@ -41,7 +47,7 @@ static int Main(string[] args)
             return rootCommand.InvokeAsync(args).Result;
         }
 
-        static int Transform(FileInfo[] templates, int lockTimeout, bool skipUpToDate, bool parallel)
+        static int Transform(FileInfo[] templates, int lockTimeout, bool skipUpToDate, bool parallel, string[] variable)
         {
             using (var locker = new Lock($"Global\\T4.Build.transform.{ComputeHash(templates)}.lock", lockTimeout))
             {
@@ -50,12 +56,13 @@ static int Transform(FileInfo[] templates, int lockTimeout, bool skipUpToDate, b
                 var didSomeWork = false;
                 var stopwatch = new Stopwatch();
 
+                var t4ParameterValues = ProcessT4ParameterValues(variable);
                 stopwatch.Start();
                 Parallel.ForEach(templates,
                     new ParallelOptions { MaxDegreeOfParallelism = parallel ? -1 : 1 },
                     t =>
                     {
-                        var generator = new BuildTemplateGenerator(t.ToString());
+                        var generator = new BuildTemplateGenerator(t.ToString(), templateContent => PreprocessTemplate(templateContent, t4ParameterValues));
                         try
                         {
                             bool skipped;
@@ -175,6 +182,42 @@ static void LogErrors(CompilerErrorCollection errors)
 
             Console.ForegroundColor = oldColor;
         }
+
+        static IReadOnlyDictionary<string, string> ProcessT4ParameterValues(string[] variableSets)
+        {
+            if (variableSets?.Any() != true)
+            {
+                return null;
+            }
+
+            var t4ParameterValues = new Dictionary<string, string>(variableSets.Length);
+            foreach (var variableSet in variableSets)
+            {
+                var pair = variableSet.Split('=', 2, StringSplitOptions.None);
+                t4ParameterValues.Add($"$({pair[0]})", pair[1]);
+            }
+
+            return t4ParameterValues;
+        }
+
+        static string PreprocessTemplate(string templateContent, IReadOnlyDictionary<string, string> t4ParameterValues)
+        {
+            if (string.IsNullOrWhiteSpace(templateContent) || t4ParameterValues?.Keys.Any() != true)
+            {
+                return templateContent;
+            }
+
+            var replacementBuilder = (StringBuilder)null;
+            foreach (var t4ParameterValuesPair in t4ParameterValues)
+            {
+                if (replacementBuilder is null && templateContent.IndexOf(t4ParameterValuesPair.Key) > -1)
+                {
+                    replacementBuilder = new StringBuilder(templateContent);
+                }
+                replacementBuilder?.Replace(t4ParameterValuesPair.Key, t4ParameterValuesPair.Value);
+            }
+
+            return replacementBuilder is null ? templateContent : replacementBuilder.ToString();
+        }
     }
 }
-
diff --git a/T4.Build/build/common.targets b/T4.Build/build/common.targets
index 7109c5c..c0a0ef1 100644
--- a/T4.Build/build/common.targets
+++ b/T4.Build/build/common.targets
@@ -22,7 +22,7 @@
 
     <Target Name="TextTemplateCreateTransformList">
         <ItemGroup>
-            <T4Build_TransformFiles Include="@(None)" Condition=" '%(None.Generator)' == 'TextTemplatingFileGenerator' " />
+            <T4Build_TransformFiles Include="@(Compile);@(None);@(Content);@(EmbeddedResource)" Condition=" '%(*.Generator)' == 'TextTemplatingFileGenerator' " />
             <T4Build_TransformFiles Include="@(TextTemplateTransformFiles)" />
         </ItemGroup>
         <ItemGroup Condition=" '$(TextTemplateTransformAll)' == 'true' ">
@@ -31,10 +31,24 @@
         </ItemGroup>
     </Target>
 
-    <Target Name="TextTemplateTransform" DependsOnTargets="TextTemplateCreateTransformList">
+    <Target Name="TextTemplateCreateParameterValueList" Inputs="@(T4ParameterValues)" Outputs="%(T4ParameterValues.Identity)">
+        <PropertyGroup>
+            <T4Build_ParameterIdentity>%(T4ParameterValues.Identity)</T4Build_ParameterIdentity>
+            <T4Build_ParameterValue>%(T4ParameterValues.Value)</T4Build_ParameterValue>
+        </PropertyGroup>
+        <PropertyGroup>
+            <T4Build_ParameterValue>$(T4Build_ParameterValue.Replace('"', '""'))</T4Build_ParameterValue>
+        </PropertyGroup>
+        <ItemGroup>
+            <T4Build_ParameterValueList Include="--variable &quot;$(T4Build_ParameterIdentity)=$(T4Build_ParameterValue)&quot;" Condition="!$([System.String]::IsNullOrWhiteSpace('$(T4Build_ParameterIdentity)'))" />
+        </ItemGroup>
+    </Target>
+
+    <Target Name="TextTemplateTransform" DependsOnTargets="TextTemplateCreateTransformList;TextTemplateCreateParameterValueList">
         <ItemGroup>
             <T4Build_TransformOptions Include="--skip-up-to-date" Condition=" '$(TextTemplateTransformSkipUpToDate)' == 'true' " />
             <T4Build_TransformOptions Include="--parallel" Condition=" '$(TextTemplateTransformParallel)' == 'true' " />
+            <T4Build_TransformOptions Include="@(T4Build_ParameterValueList, ' ')" />
         </ItemGroup>
         <Exec Command="$(T4Build_Command) transform @(T4Build_TransformOptions, ' ') @(T4Build_TransformFiles, ' ')" Condition=" '@(T4Build_TransformFiles)' != '' " ConsoleToMSBuild="true" StandardOutputImportance="normal">
             <Output TaskParameter="ConsoleOutput" ItemName="T4Build_GeneratedFiles" />