Sample Gradle, Groovy Project on IntelliJ

Change the build.gradle Add mavenLocal and right plugins...

See: The Groovy Plugin

group 'as.moes.gradletest'
version '1.0-SNAPSHOT'

apply plugin: 'java'
apply plugin: 'groovy'
apply plugin: 'idea'
apply plugin: 'jetty'
apply plugin: 'war'

repositories {
    mavenLocal()
    mavenCentral()
}

dependencies {
    compile 'org.codehaus.groovy:groovy-all:2.3.11'

    testCompile group: 'junit', name: 'junit', version: '4.11'
}