Surround the ordered list with a wrapper:

<div class="wrapper">
	<ol>
		<li>1</li>
		<li>1</li>
		<li>1</li>
	</ol>
</div>

Remove overflow: auto from the ordered list and add it to the wrapper. Make sure the wrapper has a fixed width:

.wrapper {
	overflow: auto;
	width: 30px;
}

ol {
	width: 30px;
}

li {
	display:inline-block;   
}

The wrapper should now act as a window within which the ol will scroll.

@Meta_Ing much more elegant your way :)