口语比赛的开头可以这样说：

```

Good morning/afternoon/evening, everyone!

```

接着，你可以根据比赛的具体情况和个人风格，添加一些介绍性的内容，例如：

```

Today, we gather here with great enthusiasm to participate in this exciting English speaking contest. It's not just a competition, but a platform for us to showcase our language skills and gain valuable experience.

```

或者，如果比赛是在学校环境中进行，你可以这样开始：

```

Good afternoon, dear teachers and fellow students! It's a pleasure to see such a vibrant gathering of young minds eager to express themselves in English.

```

记得在开场白结束时，可以简洁明了地介绍接下来的活动安排或比赛规则，以引导听众进入正题。