diff --git a/src/vs/workbench/api/browser/mainThreadTask.ts b/src/vs/workbench/api/browser/mainThreadTask.ts
index d94b7f3dfcb..6b25a273488 100644
--- a/src/vs/workbench/api/browser/mainThreadTask.ts
+++ b/src/vs/workbench/api/browser/mainThreadTask.ts
@@ -419,9 +419,11 @@ export class MainThreadTask implements MainThreadTaskShape {
 			if (event.kind === TaskEventKind.Start) {
 				const execution = TaskExecutionDTO.from(task.getTaskExecution());
 				let resolvedDefinition: TaskDefinitionDTO | undefined;
-				if (execution.task && execution.task.execution && CustomExecutionDTO.is(execution.task.execution)) {
-					resolvedDefinition = await this._configurationResolverService.resolveWithInteractionReplace(task.getWorkspaceFolder(),
-						execution.task.definition, 'tasks');
+				if (execution.task && execution.task.execution && CustomExecutionDTO.is(execution.task.execution) && event.resolvedVariables) {
+					const dictionary: IStringDictionary<string> = {};
+					Array.from(event.resolvedVariables.entries()).forEach(entry => dictionary[entry[0]] = entry[1]);
+					resolvedDefinition = await this._configurationResolverService.resolveAny(task.getWorkspaceFolder(),
+						execution.task.definition, dictionary);
 				}
 				this._proxy.$onDidStartTask(execution, event.terminalId!, resolvedDefinition);
 			} else if (event.kind === TaskEventKind.ProcessStarted) {
diff --git a/src/vs/workbench/contrib/tasks/browser/terminalTaskSystem.ts b/src/vs/workbench/contrib/tasks/browser/terminalTaskSystem.ts
index f6993a12c3c..e35865f75fc 100644
--- a/src/vs/workbench/contrib/tasks/browser/terminalTaskSystem.ts
+++ b/src/vs/workbench/contrib/tasks/browser/terminalTaskSystem.ts
@@ -81,12 +81,12 @@ class InstanceManager {
 
 class VariableResolver {
 
-	constructor(public workspaceFolder: IWorkspaceFolder | undefined, public taskSystemInfo: TaskSystemInfo | undefined, private _values: Map<string, string>, private _service: IConfigurationResolverService | undefined) {
+	constructor(public workspaceFolder: IWorkspaceFolder | undefined, public taskSystemInfo: TaskSystemInfo | undefined, public readonly values: Map<string, string>, private _service: IConfigurationResolverService | undefined) {
 	}
 	resolve(value: string): string {
 		return value.replace(/\$\{(.*?)\}/g, (match: string, variable: string) => {
 			// Strip out the ${} because the map contains them variables without those characters.
-			let result = this._values.get(match.substring(2, match.length - 1));
+			let result = this.values.get(match.substring(2, match.length - 1));
 			if ((result !== undefined) && (result !== null)) {
 				return result;
 			}
@@ -840,7 +840,7 @@ export class TerminalTaskSystem implements ITaskSystem {
 			}, (_error) => {
 				// The process never got ready. Need to think how to handle this.
 			});
-			this._onDidStateChange.fire(TaskEvent.create(TaskEventKind.Start, task, terminal.id));
+			this._onDidStateChange.fire(TaskEvent.create(TaskEventKind.Start, task, terminal.id, resolver.values));
 			const mapKey = task.getMapKey();
 			this.busyTasks[mapKey] = task;
 			this._onDidStateChange.fire(TaskEvent.create(TaskEventKind.Active, task));
@@ -1331,6 +1331,22 @@ export class TerminalTaskSystem implements ITaskSystem {
 			this.collectCommandVariables(variables, task.command, task);
 		}
 		this.collectMatcherVariables(variables, task.configurationProperties.problemMatchers);
+
+		if (task.command.runtime === RuntimeType.CustomExecution && CustomTask.is(task)) {
+			this.collectDefinitionVariables(variables, task._source.config.element);
+		}
+	}
+
+	private collectDefinitionVariables(variables: Set<string>, definition: any): void {
+		for (const key in definition) {
+			if (Types.isString(definition[key])) {
+				this.collectVariables(variables, definition[key]);
+			} else if (Types.isArray(definition[key])) {
+				definition[key].forEach((element: any) => this.collectDefinitionVariables(variables, element));
+			} else if (Types.isObject(definition[key])) {
+				this.collectDefinitionVariables(variables, definition[key]);
+			}
+		}
 	}
 
 	private collectCommandVariables(variables: Set<string>, command: CommandConfiguration, task: CustomTask | ContributedTask): void {
diff --git a/src/vs/workbench/contrib/tasks/common/tasks.ts b/src/vs/workbench/contrib/tasks/common/tasks.ts
index 7ec7668a9f6..a88910f481f 100644
--- a/src/vs/workbench/contrib/tasks/common/tasks.ts
+++ b/src/vs/workbench/contrib/tasks/common/tasks.ts
@@ -1067,6 +1067,7 @@ export interface TaskEvent {
 	exitCode?: number;
 	terminalId?: number;
 	__task?: Task;
+	resolvedVariables?: Map<string, string>;
 }
 
 export const enum TaskRunSource {
@@ -1078,10 +1079,10 @@ export const enum TaskRunSource {
 
 export namespace TaskEvent {
 	export function create(kind: TaskEventKind.ProcessStarted | TaskEventKind.ProcessEnded, task: Task, processIdOrExitCode?: number): TaskEvent;
-	export function create(kind: TaskEventKind.Start, task: Task, terminalId?: number): TaskEvent;
+	export function create(kind: TaskEventKind.Start, task: Task, terminalId?: number, resolvedVariables?: Map<string, string>): TaskEvent;
 	export function create(kind: TaskEventKind.DependsOnStarted | TaskEventKind.Start | TaskEventKind.Active | TaskEventKind.Inactive | TaskEventKind.Terminated | TaskEventKind.End, task: Task): TaskEvent;
 	export function create(kind: TaskEventKind.Changed): TaskEvent;
-	export function create(kind: TaskEventKind, task?: Task, processIdOrExitCodeOrTerminalId?: number): TaskEvent {
+	export function create(kind: TaskEventKind, task?: Task, processIdOrExitCodeOrTerminalId?: number, resolvedVariables?: Map<string, string>): TaskEvent {
 		if (task) {
 			let result: TaskEvent = {
 				kind: kind,
@@ -1096,6 +1097,7 @@ export namespace TaskEvent {
 			};
 			if (kind === TaskEventKind.Start) {
 				result.terminalId = processIdOrExitCodeOrTerminalId;
+				result.resolvedVariables = resolvedVariables;
 			} else if (kind === TaskEventKind.ProcessStarted) {
 				result.processId = processIdOrExitCodeOrTerminalId;
 			} else if (kind === TaskEventKind.ProcessEnded) {