Originally Posted by asu-ua772
Your leg from Los Angeles to Medford is most likely an American codeshare with Horizon, and indeed Horizon flies between LAX and MFR with the Q400. Therefore when switching between American Eagle and Horizon, you'll have to make your way to the main AA terminal (assuming your Eagle flight gets sent to the remote terminal), then leave the sterile zone and trek it over to Terminal 3, where Alaska and Horizon is located.
No - the OP can take a shuttle directly from the Eagle terminal to Terminal 3. In fact, these shuttles can be used with relative ease to do a T3-to-T4 (or vice versa) transfer, with the intermediate stop at the Eagle terminal to switch shuttles. As long as you have boarding passes or an itinerary reflecting the need to go from one terminal to another, there is no problem with doing this type of transfer.
Mike