The Category, Manufacturer and Search Results pages each have their own page layout. To make these 3 pages match you'll need to make sure that the settings and html layout for each match each other.
To start, first go to the theme you are working on.
Themes > Active Theme > Pages > Category/Manufacturer or Catalog Search page.
You'll want to make sure that the settings in the Layout section are the same across each page. Take note of these settings:
Next you'll need to copy any specific HTML from the HTML Editor:
Typically all that is required is to copy the code from within the <ac:layoutarea id="ProductList"> section.
Then go into the Settings and HTML editor for the other pages. Adjust the settings and paste your code to match.
NOTE: If other changes have been made to the page such as elements surrounding the Product List area they will need to be copied as well.