user17303: How can apply an effect to the RESULT of multiple composited clips in Final Cut Pro X? Googling all I see is how to apply the same effect to multiple clips but that's not what I'm trying to do. I'm trying to apply a single effect to the result of compositing multiple clips.
For example, one way would be to render my video without effects. Then start a new project, load the rendered video, apply the effect. It seems like I shouldn't have to render the video and start an entire new project to achieve this.
To give a simple example. Start a new project. Make the project 1280x720p, drop in a iPhone portrait mode video (make sure the project stays 1280x720p), apply the colorize event. Since the colorize event only applies to the clip I get this

But I want it to apply to the entire video (the result of all the clips)

Note I am not try to achieve the effect shown above. I just needed to throw together an example showing the issue (effect applies to clip instead of to entire video).
Is there a way to do it short of rendering out the entire video, starting a new project and applying the effects to the rendered video?

user20675: I’m not entirely sure what you explain. However I try. 
Did you look into the option of an adjustment layer?
http://www.fcp.co/final-cut-pro/tutorials/945-how-to-build-and-use-adjustment-layers-in-final-cut-pro-x

user19533: I can't see your timeline so I'm not sure if this might help too: 
I think you can select all clips within the timeline and than group them (alt + g) to a compound clip. This way you can add effects onto the compound layer and it will be placed on all.

17303: <p>How can apply an effect to the RESULT of multiple composited clips in Final Cut Pro X? Googling all I see is how to apply the same effect to multiple clips but that's not what I'm trying to do. I'm trying to apply a single effect to the result of compositing multiple clips.</p>

<p>For example, one way would be to render my video without effects. Then start a new project, load the rendered video, apply the effect. It seems like I shouldn't have to render the video and start an entire new project to achieve this.</p>

<p>To give a simple example. Start a new project. Make the project 1280x720p, drop in a iPhone portrait mode video (make sure the project stays 1280x720p), apply the colorize event. Since the colorize event only applies to the clip I get this</p>

<p><a href="https://i.stack.imgur.com/s2k4c.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/s2k4c.png" alt="enter image description here"></a></p>

<p>But I want it to apply to the entire video (the result of all the clips)</p>

<p><a href="https://i.stack.imgur.com/VPwoK.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VPwoK.png" alt="enter image description here"></a></p>

<p>Note I am not try to achieve the effect shown above. I just needed to throw together an example showing the issue (effect applies to clip instead of to entire video).</p>

<p>Is there a way to do it short of rendering out the entire video, starting a new project and applying the effects to the rendered video?</p>
 20675: <p>I’m not entirely sure what you explain. However I try. 
Did you look into the option of an adjustment layer?
<a href="http://www.fcp.co/final-cut-pro/tutorials/945-how-to-build-and-use-adjustment-layers-in-final-cut-pro-x" rel="nofollow noreferrer">http://www.fcp.co/final-cut-pro/tutorials/945-how-to-build-and-use-adjustment-layers-in-final-cut-pro-x</a></p>
 19533: <p>I can't see your timeline so I'm not sure if this might help too: </p>

<p>I think you can select all clips within the timeline and than group them (alt + g) to a compound clip. This way you can add effects onto the compound layer and it will be placed on all.</p>
