Turnout has many health benefits for horses, but if your horse is difficult to catch, it can be tempting to keep him in a stall. With a little patience, and maybe changing your approach, catching your horse may become a little easier. Don't expect miracles on the first day, but if you make some adjustments to what you are doing, you may be surprised at the change in your horse's behavior.
Enter the pasture with the halter and lead rope over your shoulder, ready to slip on your horse's head. Make sure everything is untangled and ready to go. Ideally, you should walk up to your horse, slide your arm around his neck, from under the jaw around and over his ears, and hold him steady while you slip the halter on. If the halter is tangled, the buckles aren't unfastened, or the lead rope is tangled through the halter, you won't be able to do this, and your horse may wander off while you're sorting out your equipment.
Approach With Care
Walking directly up to your horse, approaching from the front and staring at him, probably will send a difficult to catch horse to the other side of the pasture. You may think you appear confident and in charge, but your horse may find you intimidating, which will trigger his fight or flight instinct. Instead, approach him by walking alongside him, getting as close as possible without him moving away. If you can get close enough to place your hand on his shoulder, you probably can catch him. Stop anytime he shows signs of moving away. You also may have some luck by crouching down. He may find your lower stance interesting and approach you out of curiosity.
Walk Him Down
Never chase your difficult to catch horse. You have no chance of running as fast as him, and you simply will reinforce in his mind the idea that he should run away. Instead, dedicate the time to walk him down. Follow him around the pasture at a leisurely pace, trying to approach him when he stops, and following him at a walk when he moves away. Don't yell at him, swing the halter or lead rope around, or otherwise lose your cool. Eventually, he will get tired of the game and let you approach him. You may have to walk him down several days in a row, but soon he will learn that you are more persistent than he is, and he will wait for you to catch him, or even walk up to you when he sees you approach.
Regardless of how long it took you to walk your horse down, once you catch him, reward him with a pat and praise. Once you have him out of the pasture, you may want to hand graze him in an otherwise off-limit spot or give him some other treat. Never punish him once you catch him, and don't immediately saddle him up and work him. The important thing is to teach him that what happens with you, outside the pasture, is more enticing than trying to avoid you in the pasture.