If table-cell
is an option, here’s a way to do it:
.container {
display: table;
width: 100%;
padding: 5px;
border: 1px solid black;
}
.container .column {
display: table-cell;
width: 40%;
background-color: #AAA;
padding: 5px;
border: 5px solid white;
vertical-align: top;
height: 100%;
}
select {
width: 100%;
}
<div class="container">
<div class="column">Stretch to fill?</div>
<div class="column">
<select size="15">
<option>Option 1</option>
<option>Option 2</option>
</select>
</div>
<div>