You can make post loop as list item by using following action hooks
add_action('post_grid_before_loop', 'post_grid_before_loop_ol_start');
function post_grid_before_loop_ol_start(){
?>
<ol>
<?php
}
add_action('post_grid_loop', 'post_grid_loop_li_start', 5);
function post_grid_loop_li_start($args){
?>
<li>
<?php
}
add_action('post_grid_loop', 'post_grid_loop_li_end', 90);
function post_grid_loop_li_end($args){
?>
</li>
<?php
}
add_action('post_grid_after_loop', 'post_grid_after_loop_ol_end');
function post_grid_after_loop_ol_end(){
?>
</ol>
<?php
}